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DESCRIPTIVE  ANATOMY 


WM.  B.  TOWLES, 


FORMER  Professor  of  Anatomy  in  the  University  of  Virginia 
AND  IN  THE  University  of  Vermont. 


REVISED  AND  ENLARGED 

BY 

W.  G.  CHRISTIAN, 
present  Professor  of  Anatomy  in  the  University  of  Virginia. 


ANDKRSON  BROS.,  PUBLISHERS, 

University  of  Virginia. 

1898. 


u 


COPYRIGHT, 
1898, 

BY 

ANDERSON  BROS. 


i\VVE_P/?^V7. 


PREFACE. 

Towles'  Notes  on  Anatomy,  which   forms  the  basis  of  the 
present  work    was  not  the  work  of  a  single  man,  but  the  out- 
growth of  a  school.     This  school,  founded  here,  probably,  by 
Prof.  Robley  Dunghson,  who  brought  the  Edinburgh  tradi- 
tions into  his  teaching,  was   perfected   by   Prof.  John   Staige 
JJavis,  who,  in  his  turn,  instructed  Prof.  Towles,  from  whom 
the  present   writer  acquired    what   knowledge  of  anatomy  he 
possesses      The    effort  of  all  of  the   teachers  in   this  school 
has  been  to  make  the  instruction  clear,  simple,  and  practical  ; 
and  these  have  been  the  characteristics  of  the  Notes       While 
endeavoring  to  increase  the  amount  of  information  contained 
m  the  work  and  to  make  it  more  representative  of  the  lectures 
the  writer  has  tried  to  preserve  those  characteristics  which 
have  alw^a3^s  distinguished  the  School  of  Anatomy  at  the  Uni- 
versity of  Virginia.     At  this  late  day  it  is  impossible  for  any 
one  towrite  an  original  work  on  such  a  subject  as  anatomy, 
and  originality  is  not  claimed  for  this  work.     It  has  simply 
been  the  writer's  purpose   to  adopt  the    best,  in  his  opinion 
trom  all  of  the  other  writers  he  has  been  able  to  read  ;   but  at 
the  same  time,  no  statement  has  been  made  in  this  book  which 
has  not  been  verfied   by  dissection. 

The  effort  has  been  made  to  make  this  a  student's  book  •   it 
IS  not  intended  to  imitate  those  works  which  are  designed  for 
practitioners  and  students  alike.     In  the  opinion  of  the  writer 
a  successful    work   of  the  kind    last   mentioned   is  a  manifest 
impossibility,  the   needs  of   the  student  and  the   needs  of  the 
practitioner  being  entirely  dissimilar.     It  has  been  the  inten- 
tion in  this  work  to  give  to  the  student  a  clear,  complete  state- 
ment of  the  positive  truths  of  anatomy,  leaving  embrvology 
and    histology,  so  largely  treated  in  other  works,  to  the  care 
of  the  professors  of  these  subjects.      The  writer  has  discussed 
neither    surgery    nor    practice    of    medicine,    but   descriptive 
anatomy,  pure  and  simple,  in  such  a  way  as  the  needs  ..f  the 
student  demand. 

Universily  of  Virgima.  W.  G.  Christian. 

Aiig^ist,  i8g8. 


DESCRIPTIVE  ANATOMY. 


OSTEOLOGY. 

fj^-  d'"^/  °n  *'  ^"''  '"^'"^  ^°  '°  f"^™  the  human  skele- 
ton    md.vxdually  and  ,n   relation  to  one  another,   with  re<.ard 
to  the  appearaiices  which  they  present  to  the  unaided  eve   and 
he  uses  for  wh.ch  they  are  intended,   constitutes  Osteo  o  " 
as  perta,n,n^  to  Descriptive    Anatomy.     The  chief  uses    of 

tissues.  2d.  To  form  receptacles  for  important  organs.  3d 
To  form  uny.eld.n^    points  of  attachment  for  the   muscles: 

n!ayb?utni7ed.^^    '''''''   '''°''''   -'''''    "---    -tion 
In  order  to  fulfill  these  functions,  bones  present  manydiffer- 

mto.  1st.  Long  Bones,  when  the  extension  in  one  direction 
Srreatly  exceeds  that  in  the  other.  2d.  Plat  Bones,  when  he 
extension   ,n  two  directions  greatly  e.xceeds  that  i^  the  olher 

relation  to  other  Jnes.     2d.  Th^e^'cTass  tf  wl^ch^  ifb:!::^ 
3d.  &,veadescr,pt,on  of  the  appearances  on  the  bone:  whethe 
here   be  surfaces,  borders,  extremities,  shaft,  depressions  or 
elevafons,  and  especially  note  any  articular  surface   thalis  a 

nect.on    ,t  ,s  proper  to  explain  two  technicalities  of  frequent 
use -Internal    and    External-these   terms    should    be    used 
w.th  reference  to  the  middle  line  or  plane  of  the  body,  that  is 
ne  object  >s  ,„ternal  to  another  because  it  is  nearer  th'   midd 
cav^'tv      .  ''•  ""  f ""   "'"'  '"-■-■•ectly   with   reference  to  a 

The'  bo  ^",    T""'  """^  '"'  '^™^  '"  "e  here  emoloyed. 

The  bones  are  d,v,ded  into  those  of  the  vertebral  column    o 
e  Thorax:  of  the  Upper  Extremity:  of  the  Lower  Extremity 
of  the  skull;  the  Os  Hyoides;  the  Ossicula  Auditus 


DESCRIPTIVE  ANATONY. 


The  Vertebral  Column. 


The  vertebral  column  or   spine,  consists  of  a  series  of  sep- 
arate bones,  classed  as  irregular,  called  vertebra,  and  extends 
from  the  base  of  the  skull  to  the  lower  termination  of  the 
TDelvis      It  is  flexuous  in  direction  and  of  unequal  size  at  dit- 
ferent  places,  smallest  in  the  neck,  it  gradually  enlarges  to 
below   its   middle  and  then   suddenly    tapers  to  a  point     it 
transmits  the   weight  of   the  head  to  the  lower    extremities, 
o-ivino-  support  on   each  side  to  the  bones  which  enclose  the 
thoracic  cavitv,  and  indirectly  to  those  of  the  upper  extremities. 
Towards  its  lower  termination  it  has  expanding  from  it  on 
either  side  the  bones  which  form  the  pelvis.     It  forms  the  re- 
ceptacle for  the  spinal  marrow  and  its  envelopes.     In  the  adult 
it  consists  of  twenty-six  pieces,   called  vertabras,   which  are 
divided  into  four  classes;   in  the  neck  they  are  called  cervical 
vertebrae,  and  are  seven  in   number: 

In  the  Thoracic  region— Dorsal— twelve  in  number. 
In  the  Abdominal  region— Lumbar— five  in  number. 
In  the  Pelvic  region— Pelvic— two  in  number. 
The  last  are  known  as  sacrum  and  coccyx,  and  before  adult 
life  are  composed  of  nine  pieces-the  sacrum  having  five  and 
the  coccyx  four.     The  vertebra  of  the  different  regions  have 
characteristics   which   distinguish  them   from  those  of  other 
reo-igns,  and  each  vertebra  certain  less  noticeable  ones  which 
designate  its  position  in   its  own  region.     Kach  region,  how- 
ever, possesses  one  or   more  bones  so  widely  different  from 
the  typical  vertebra  of  that  region  as  to  deserve  the  appellation 
of  "Peculiar." 

Since  there  are  appearances  common  to  the  vertebrae  ot  all 
regions,  these  must  be  first  noted. 

Vertebra. 

Kach  vertebra  consists  of  the  following  parts  :  1st,  Body  ; 
2i,  Foramen  for  the  spinal  cord;. 3d,  Lamina  (2);  4th,  Pedicles 
(2)';  5th,  Spinous  process  ;  6th,  Transverse  Processes  (2) ;  7th, 
Articular  Processes  (4);  8th,  Intervertebral  Notches  (4). 


OSTEOLOGY.  3 

]st.  The  Body  is  the  front,  thick,  massive  portion  of  the 
bone,  flattened  above  and  below  to  articulate  with  adjoining- 
bones,  indirectly  by  the  intervention  of  cartilag-e  ;  it  is  more 
or  less  circular  in  outline  and  slig-htly  flattened  behind  ;  the 
edg-es  project  somewhat  in  front  and  laterally,  so  as  to  produce 
a  furrow  on  the  front ;  its  posterior  aspect  forms  the  anterior 
boundary  of  the  spinal  foramen. 

2d.  The  Spinal  Foramen  lies  between  the  body  in  front  and 
the  spinous  process  behind,  and  is  bounded  laterally  by  the 
lamina.  It  is  a  large  opening-,  varying-  in  form  and  size  in  the 
different  regions. 

3d.     The  Lamina  spring-s,  one  each  side,  from  the  postero- 
lateral aspect  of  the  body,  throug^h  the  medium  of  the  pedicle, 
and  arches  back  to  meet  its  fellow  to  form  the  spinous  process 
thus  inclosing  the  spinal  foramen.     It  is  flattened  from  side  to 
side,  and  presents  an  upper  and  a  lower  border. 

4th.  The  pedicle  is  the  more  or  less  rounded  commencement 
of  the  lamina. 

5th.  The  Spinous  Process  juts  backward  from  the  union 
of  the  two  laminae. 

6th.  The  Transverse  Process  projects  laterally  from  near 
the  anterior  extremity  of  the  lamina  on  either  side. 

7th.  The  Articular  Processes  are  four,  two  superior  and 
two  inferior.  They  extend  upward  and  downward  from  the 
lamina. 

8th.  The  Intervertebral  Notches  are  four,  two  superior 
and  two  inferior  ;  they  are  furrows  on  the  upper  and  lower 
aspects  of  the  pedicles. 

Cervical  Vertebra. 

The  discrimination  of  a  Cervical  Vertebra  involves  the  fol- 
lowing- points:  it  is  the  smallest;  its  body  is  smallest,  having- 
its  transverse  diameter  g-reater  than  the  antero-posterior ;  on 
its  upper  aspect  the  lateral  edges  are  raised  into  ridg-es.  The 
spinal  foramen  is  larg-est  and  is  triangfular.  The  lamina  is 
narrow  and  long-.  The  spinous  process  is  triang-ular  and 
bifid  at  the  extremity,  g-enerally.  The  transverse  process  is 
perforated  at  its  base  by  an  opening-  called  the  vertebral  fora- 


4  DESCRIPTIVE  ANATOMY. 

men,  is  grooved  above  and  bifid  at  its  extremity,  forming-  two 
nodules  which  are  called  the  anterior  and  posterior  tubercles  of 
the  transverse  processes.  The  Articular  processes  are  oblique  ; 
the  superior  face  upward,  inward  and  backward,  the  inferior 
downward,  forward  and  outward. 

Dorsal  Vertebra. 

To  discriminate  a  typical  Dorsal  Vertebra  the   following- 
appearances  must  be  noted: 

The  body  is  intermediate  in  size  betw-een  that  of  a  cervical 
and  a  lumbar  vertebra  ;  there  is  no  g"reat  preponderance  of  the 
one  diameter  over  the  other  ;  althoug-h  in  the  upper  part  of  the 
reg"ion  the  transverse  is  slig-htly  g-reater,  and  in  the  middle 
portion  the  antero-posterior.  The  most  characteristic  feature 
is  the  appearance,  on  the  postero-lateral  aspect  of  the  body,  of 
articular  half-facets,  situated,  two  on  each  side,  at  the  upper 
and  lower  borders  :  these  are  for  the  reception  of  the  heads  of 
the  ribs.  The  spinal  foramen  is  smaller  than  in  the  other  re- 
g-ions,  and  is  nearly  round.  The  lamina  is  short,  slopes 
obliquely  from  behind,  upward  and  forward,  and  is  almost 
entirely  covered  by  the  orig-in  of  the  processes  which  spring- 
from  it.  The  pedicle  is  deeply  notched  inferiorly.  The 
spinous  process  is  triang-ular,  and  is  disting-uished  from  that 
of  a  cervical  vertebra  by  not  being-  bifid,  it  extends  downward 
and  slig-htly  backward.  The  transverse  process  is  peculiarly 
well  marked,  being-  large,  long-  and  extending-  outward  and 
backw^ard,  increasing-  in  size  as  it  removes  from  its  orig-in  so 
as  to  present  an  enlarg-ement  at  its  termination  ;  that  is,  it  is 
"clubbed."  It  bears  on  its  anterior  face,  near  its  termination, 
an  articular  facet.  The  superior  articular  processes  are  ver- 
tical and  look  from  each  other,  outward  and  backward  ;  the 
inferior  are  opposite. 

A  Lumbar  Vertebra. 

In  the  lumbar  reg-ion  the  whole  bone  is  more  massive  than 
in  the  cervical  and  dorsal  reg-ions.  The  body  is  larg-e,  its 
transverse  diameter  g-reater  than  the  antero-posterior.  Its 
anterior  surface  is  concave  from  above  downward,  convex  from 


OSTEOLOGt".  5 

side  to  side,  slightly  lipped  above  and  below.  The  superior 
and  inferior  faces  present  a  concave  central  portion  with  an 
elevated  circumference.  The  posterior  face  althoug-h  nearly 
flat,  presents  a  slig^ht  concavity  from  above  downward  and 
from  side  to  side  with  larg-e  opening's  for  the  veins.  No 
lateral  articular  facets  are  seen  on  the  body.  The  spinal 
foramen  is  obscurely  triangular  and  is  intermediate  in  size 
between  the  larg-e  cervical  and  small  dorsal.  The  pedicles 
are  short  and  thick,  project  nearly  backward  with  but  a  slight 
inclination  outward  and  are  marked  below  by  deep  and  wide 
intervertebral  notches.  The  superior  notches  are  narrow  and 
shallow.  The  laminae,  short  and  massive,  pass  downward 
backward  and  inward  to  join  the  spinous  process,  and  are 
partly  hidden  by  processes.  The  spinous  process  is  nearly 
quadrilateral,  strong  and  thick.  It  projects  straight  back- 
ward and  terminates  in  a  blunt,  rough  almost  clubbed  extremity. 
The  transverse  processes  spring  from  the  junction  of  the  body 
and  pedicles.  They  are  long  narrow,  thin  and  curved,  resem- 
bling a  rib  in  shape.  They  pass  backward  and  outward  with 
a  slight  inclination  upward.  The  superior  articular  processes 
are  cut  nearly  vertically,  as  in  the  dorsal  region,  but,  unlike 
the  latter,  face  toward  each  other  so  that  their  direction  is 
backward  and  inward.  They  are  concave  from  before  back- 
ward to  receive  the  inferior  processes,  and  are  situated  at  the 
junction  of  the  pedicles  and  laminae.  The  inferior  processes, 
situated  entirely  on  the  laminae,  are  vertical,  convex  from  be- 
fore backward  and  face  outward  and  forward  so  as  to  be 
received  between  the  inverted  superior  processes. 

Peculiar  Vertebrae. 

The  foregoing  description  of  a  vertebra  in  each  region  is,  as 
stated,  of  one  typical  of  that  region  ;  and  this  typical  vertebra 
is  one  from  about  the  middle  of  that  region.  Toward  the  con- 
fines of  each  region  the  vertebrae  partake  more  or  less  of  the 
characters  of  vertebrae  in  the  adjoining  regions,  and  so  far 
depart  from  the  type  as  to  deserve  the  appellation  "Peculiar" 
— thus  demanding  a  special  description.     The  departure  from 


6  DESCRIPTIVE  ANATOMY. 

the   typical  vertebra  is   so   g-reat  in  some  instances  that  the 
bones  have  received  special  names. 

In  the  cervical  region  there  are  three  peculiar  vertebrae — ■ 
the  first,  second  and  seventh. 

The  First  Cervical  Vertebra,  or  Atlas. 

This  vertebra  is  known  as  the  Atlas  because  it  supports  the 
weig-ht  of  the  head  ;  it  resembles  only  in  a  slig-ht  deg-ree  a  ty- 
pical vertebra,  having  no  body  and  being-  scarcely  more  than 
a  ring-  of  bone.  It  is  described  as  consisting-  of  four  parts — 
two  arches  and  two  lateral  masses — surrounding- a  spinal  fora- 
men of  remarkable  size — much  larg-er  than  in  any  other  verte- 
bra. 

The  lateral  masses  stand  one  on  each  side,  being-  connected 
before  and  behind  by  the  anterior  and  posterior  arch.  The 
anterior  arch  is  much  shorter  than  the  posterior,  and  forms 
one-fifth  of  the  circumference  of  the  bone  ;  it  presents  on  the 
middle  of  its  front  an  elevation, called  the  anterior  tubercle  of  the 
Atlas  and  opposite  this,  on  the  posterior  face  of  the  anterior 
arch,  is  a  circular,  concave  articular  facet  for  the  o^Ojitpid 
process  of  the  next  vertebra. 

The  ppsterior  arch  forms  about  two-fifths  of  the  circumfer- 
ence of  the  bone.  It  is  convex  and  rough  behind,  presenting 
in  the  mid  line  a  slig-ht  rough  eminence  called  the  posterior 
tubercle  of  the  Atlas, a  rudimentary  spinous  process.  The  upper 
bordler  of  the  posterior  arch  presents,  jjist  behind  the  lateral 
mass,  a  deep  groove  or  notch,  the  superior  intervertebral  notch 
and  below,  behind  the  inferior  articular  process,  a  similar  but 
slighter  groove,  the  inferior  intervertebral  notch.  It  will  be 
seen  that  the  intervertebral  notches  are  behind  the  articular 
processes  in  this  vertebra  instead  of  being  in  front  as  in  a 
typical  vertebra. 

Kach  lateral  mass  forms  about  one-fifth  of  the  bony  circle, 
and  sustains,  above  and  below,  the  articular  processes.  The 
superior  are  oval,  concave,  oblique,  articular  pits,  whose  long 
diameter  is  directed  from  in  front  backward  and  outward  ap- 
proaching each  other  more  nearly  in  front  than  behind,  ^d 
looking  upward,  inward,   and  forward.     About  their  middle 


OSTEOLOGY.  7 

they  are  frequenty  slig-htly  encroached  upon  by  the  non-articu- 
lar portion  of  the  bone  so  as  to  g-ive  them  something-  of  a  kid- 
ney shape.  The  inferior  processes  are  smaller,  circular, 
slightly  concave  or"Hat  and  directed  downward,  inwar3  and 
slightly  backward.  The  inner  face  of  each  lateral  mass  is 
marked,  just  below  the  superior  articular  process,  by  a  slight 
tu'Bercle  intended  for  ligamentous  attachment.  The  trans- 
yerse  processes  project  outward  and  a  little  downward.  They 
are  large  and  prominent,  perforated  at  the  base  but  not 
marked  by  either  groove  or  tubercle  as  in  the  typical  vertebra. 

The  Second  Cervical  Vertebra,  or  Axis. 

The  body  of  the  Atlas  becomes  ossified  to  the  Axis  and  ap- 
pears on  that  bone  as  the  odontoid  process.  This  process  occu- 
pies the  whole  of  the  upper  surface  of  the  Axis,  springing  by 
a  slightly  constricted  portion  called  the  neck,  ascending*  and 
enlarg-ing"  for  a  short  distance  to  again  decrease  and  finally  ter-^T' 
minate  as  a  blunt  point.  On  either  side,  just  below  the  termi-^ 
nation,  there  is  a  rough  depression  for  ligamentous  attach- 
ment. Below  this  and  on  its  anterior  face,  is  a  smooth  circu- 
la'f,  convex  articular  facet  tcLplay  oji  a  similar  surface  on  the 
rfffteriof  arch  of  the  Atlas.  Ju-st  opposite  to  this,  on  the  pos- 
terior surface,  is  a  second  smooth  surface  fgir  the  play  of  the 
transverse  ligament.  "T^he  tjody  is  marked  in  front  by  a  verti- 
cal ridge  and  on  either  side  of  this  by  deep  depression.  The 
superior  articular  facets  appear  to  be  seated  on  the  junction  of 
the  pedicles  and  body.  They  are  circular  in  form,  nearly  flat 
and  face    upward    and  outward,   possibly    slightly    forward. 

The  transervse  processes,  less  prominent  than  those  of  the 
Atlas,  are  not  bifid  and  pass  downward  and  outward.  The}'' 
are  pierced  by  the  vertebral  foramen,  which  runs  from  below 
upward  toward  the  superior  articular  facet  and  then  turns  ab- 
ruptly outward,  forming  nearly  a  right  angle.  The  laminae 
are  thick  and  strong-  ;  the  spinous  process,  strong-  and  thick, 
projects  straight  backward,  is  deeply  g-rooved  on  its  under  sur- 
face and  frequently  bifurcated  at  the  extremity.  There  is 
barely  a  trace  of  a  superior  intervertebral  notch,  which,  when 
present,  lies  behind  the  articular  process.     The  lower  portion 


8  DESCRIPTIVE  ANATOMY. 

of  the  bone  presents  the  characteristics  of  a  typical  cervical 
vertebra,  but  is  more  massive. 

Vertebra  Prominens,  or  Seventh  Cervical  Vertebra. 

This  vertebra  derives  its  sobriquet  of  prominens  from  its 
possession  of  a  remarkably  long-,  thick,  uon  bifid,  spinous 
process,  which  disting-uishes  it  from  the  other  cervical  verte- 
brae. It  is  also  larg-er  than  the  other  vertebrae  of  this  region, 
its  spinal  foramen  is  smaller  and  the  lower  surface  of  the 
body  is  more  like  that  of  a  dorsal  vertebra. 

Peculiar  Dorsal  Vertebrae. 

The  peculiar  dorsal  vetebrae  are  the  first,  ninth,  tenth, 
eleventh  and  twelfth. 

The  /i}'st  presents  on  each  side  of  its  body,  above  andpostero- 
laterally,  a  whole  facet  for  the  head  of  a  rib  ;  below,  in 
corresponding  position,  a  half  facet  on  each  side.  The  ninth 
has  but  one  demi-facet  on  each  side,  which  is  on  the  upper 
border.  The /^;z//^  has  one  whole  facet  on  each  side  above.  The 
eleventh  has  one  whole  facet  on  each  side',  but  its  transverse 
process  has  no  articular  facet.  The  tzvelfth  has  one  whole 
facet  on  each  side  ;  its  transverse  process  has  no  articular  facet 
and  its  inferior  articular  processes  are  everted. 

The  Pelvic  Vertebrae. 

The  pelvic  vertebrae,  specifically  known  as  sacrum  and 
coccyx,  form  the  lower  part  of  the  vertebral  column,  and 
derive  the  appellation  of  pelvic  from  the  fact  that  they  form 
the  posterior  wall  of  the  pelvis  in  the  articulated  skeleton. 
They  are  described  separately. 

Sacrum  (Sacer-Sacred.) 

The  sacrum  lies  between  the  fifth  lumbar  vetebra  above 
and  the  coccyx  below,  and  between  the  two  ossa  innominata. 
It  is  triangular  in  outline,  its  base  being-  upward  and  its  trun- 
cated apex  below  and  backward  and  tipped  by  the  coccyx. 
Its  anterior  face  is  concave,  both  from  above  downward  and 
from  side  to  side,  more  so  in  men  than  in  women,  this  being- 
one    means    of   disting-uishing-   the    sex   to    which    the    pelvis 


OSTEOLOGY.  9 

belonofed.  It  is  described  as  consisting-  of  an  anterior  and 
posterior  face,  two  lateral  borders,  a  base  and  an  apex. 

The  anterior  face  is  concave  and  presents  two  vertical  rows 
of  foramina,  of  four  each,  one  row  on  each  side  of  the  middle 
line,  called  the  anterior  sacral  foramina  ;  the  upper  two  in 
each  row,  are  considerably  larg-er  than  the  lower  two.  Con- 
necting- each  foramen  with  the  corresponding-  one  in  the 
opposite  row  is  a  ridge  ;  these  ridg-es  marking-  the  line  of 
union  of  the  five  separate  vertebra?  of  which  the  sacrun  con- 
sisted in  the  3'oung-  subject.  Passing-  outward  from  each 
foramen  is  a  groove  for  a  sacral  nerve. 

The  posterior  face  of  the  sacrum  is  narrower  than  the  ante- 
rior, is  convex  both  from  above  downward  and  from  side  to 
side  and  is  rough.  Above,  in  the  mid  line,  is  seen  the  trian- 
gular opening-  of  the  spinal  canal  ;  below  this  is  a  row  of 
roug-h  projections,  the  rudimentary  spinous  processes.  The 
upper  two  of  these  are  usually  distinct,  while  tlje  two  lower 
coalesce.  •  The  lower  spine  is  wanting-  and  here  the  spinal 
canal  is  exposed.  External  to  the  sacral  supines  is  seen  a  row 
of  slig-ht  projections,  the  rudimentary  articular  processes, 
and  between  these  and  the  spines  is  a  vertical  g-roove,  the 
sacral,  continuous  with  the  vertebral  g-roove  above.  Exter- 
nal to  the  articular  tubercles  is  a  row  of  foramina,  less  reg-u- 
lar  in  outline  and  smaller  in  size  than  those  on  the  front,  the 
posterior  sacral  foramina,  four  in  number  like  those  on  the 
anterior  face.  External  to  these  again,  and  nearly  on  the 
lateral  border,  is  another  row  of  roug-h  tubercles,  the  rudimen- 
tary transverse  processes. 

The  lateral  borders,  broad  and  thick  above,  narrow,  thin 
and  roug-h  below,  present  superiorly  and  anteriorly  a  long-, 
ear-shaped  articular  facet  for  the  os  innominatum,  behind  this 
a  deep  rough  depression  for  ligamentous  attachment. 

The  base,  or  upper  extremity,  presents  in  the  mid  line  an 
oval  articular  surface,  corresponding  in  shape  and  size  to  the 
lower  surface  of  the  last  lumbar  vertebra,  with  which  it  arti- 
culates. On  either  side  of  this  is  a  broad,  smooth  expanded 
surface,  called  the  wing  of  the  sacrum.     Behind  the  articular 


10  DESCRIPTIVE  ANATOMY. 

surface  is  seen  the  triangular  upper  opening-  into  the  sacral 
canal,  a  continuation  of  the  spinal  canal.  This  canal  passes 
through  the  sacrum,  decreasing  in  size  as  it  descends,  and  is 
open  posteriorly  below  on  account  of  the  absence  of  the  last 
spinous  tubercle  of  the  sacrum.  On  either  side  of  the  opening 
is  an  articular  process.  These  processes,  like  the  superior 
articular  processes  of  a  lumbar  vertebra,  face  toward  each 
other.  In  front  of  the  articular  processes  on  either  side  is  a 
groove  corresponding  to  the  intervertebral  notch  of  other  ver- 
tebra. 

The  apex,  or  lower  extremity  of  the  sacrum,  presents  an 
oval  surface  for  articulation  with  the  coccvx,  and  on  either 
side  of  this  an  articular  nodule,  called  the  cornu.  Behind  the 
oval  surface  is  the  opening  of  the  sacral  canal  which  terminates 
the  spinal  canal. 

Coccyx. 

The  coccyx  forms  the  lower  extremitv  of  the  vertebral 
column;  it  originally  consists  of  four  pieces  or  verte- 
brae united,  in  the  adult,  into  one  bone,  which  is  sometimes 
ossified  to  the  sacrum.  It  is  triangular  in  shape;  its  base  is 
above,  presenting  an  oval  articular  facet  for  the  truncated  apex 
of  the  sacrum;  its  apex  is  below  and  forward  the  bone  con- 
tinuing the  curve  of  the  sacrum  and  frequently  deviating  to 
one  side. 

The  Vertebral  Column  as  a  Whole. 

Viewed  as  a  whole  the  vertebral  column  presents  two  pyra- 
mids with  their  bases  opposed,  the  superior  pyramid  being  com- 
posed of  all  the  vertebra  from  the  second  cervical  to  the  last 
lumbar,  the  inferior  consisting  of  the  nine  pelvic  vertebra. 
On  more  careful  examination  it  will  be  found  that  the  supe- 
rior pyramid  may  itself  be  divided  into  three,  one  extending 
from  the  second  cervical  to  the  first  dorsal,  the  second  from 
the  first  to  the  fourth  dorsal,  base  upward,  and  the  last  con- 
sisting of  the  remaining  vertebra  with  the  base  at  the  fifth 
lumbar.  These  smaller  pyramids  are  comparatively  unimpor- 
tant. Although  the  general  direction  of  the  vertebral  column 
is  vertical,  it  does  not  present  a  straight  line.     In  the  cervical 


OSTEOLOGY.  11 

reg"ion,  and  including*  the  first  and  second  dorsal  vertebras,  it 
is  convex  forward,  in  the  dorsal  concave  forward,  in  the  lumbar, 
convex  and  in  the  pelvic  ag-ain  concave  forward.  Thus  it  will 
be  seen  to  consist  of  alternate  compensatory  antero-posterior 
curves,  an  increase  in  the  curvature  of  one  reg-ion  always 
causing-  a  corresponding*  compensation  in  the  reg^ion  below. 
Viewed  from  the  front  we  see  the  convex  bodies  of  the  vertebrse, 
marked  by  their  transverse  g^rooves  and  separated  by  the 
intervertebral  disks,  the  whole  presenting-  the  curvatures  above 
described.  Posteriorly,  in  the  mid  line,  will  be  seen  the  spi- 
nous processes,  rudimentary  in  the  first  cervical,  prominent  in 
the  second,  decreasing-  in  size  until  the  sixth  is  reached,  well 
marked  and  prominent  in  the  seventh  and  even  more  prominent 
in  the  first  dorsal.  From  this  point  the  spines  become  long-er 
in  the  dorsal  region  until  the  ninth  is  reached,  but,  owing-  to 
their  downward  inclination,  less  prominent.  Ag-ain  prominent 
and  projecting-  backwards  in  the  lumbar,  they  become  indis- 
tinct in  the  upper  sacral  and  disappear  entirely  in  the  lower 
sacral  reg-ion.  Sometimes  there  are  normal  deviations  from 
the  mid  line  even  in  health,  so  that  the  spines  do  not  form  a 
straig-ht  line  down  the  back.  On  either  side  of  the  spines  is 
seen  a  g-roove  which  is  broad  and  shallow  in  the  cervical, 
deep  in  the  dorsal  and,  becoming-  less  marked  in  the  lumbar, 
finally  disappears  in  the  lower  pelvic  reg-ion.  Laterally  may 
be  seen  the  sides  of  the  bodies  of  the  vertebrae,  presenting-  in 
the  cervical  reg-ion  the  transverse  processes,  g-rooved  by  the 
intervertebral  foramina  ;  intervertebral  foraminaand  transverse 
processes  with  articular  facets  for  ribs,  in  the  dorsal  ;  and 
similar  foramina  and  spine-like  transverse  processes  in  the 
lumbar  reg-ion.  The  pelvic  reg-ion  shows  the  lateral  border  of 
the  sacrum  and  coccyx. 

The  length  of  the  vertebral  column  varies  at  different 
periods  of  life  and  in  different  individuals.  In  the  adult  it  is 
from  twenty-four  to  twenty-eig-ht  inches  long-. 

Sternum. 

The  sternum  or   breast  bone,  forms  the  middle  portion  of 
the  tho.racic  wall  in  front,  the  dorsal  vertebras  occupying-  the 


12  DESCRIPTIVE  ANATOMY. 

mid-line  behind;  connecting*  these  on  each  side  are  the  ribs, 
which  are  prolong-ed  by  the  costal  cartilages.  Kxtending-  out- 
ward from  the  upper  end  of  the  sternum  on  each  side  is  the 
clavicle.  The  direction  of  the  long*  axis  of  the  sternum  is 
downward  and  forward.  Originally  consisting  of  six  parts, 
these  in  the  adult  become  united  into  three — the  upper  or 
Manubrium,  the  middle,  or  Gladiolus,  and  the  lower,  E)nsi- 
form  or  Xiphoid  cartilage.  These  are  united  by  cartilage, 
but  later  in  life  may  become  ossified  together,  the  ensiform 
cartilage  frequently  becoming  ossified  and  firmly  united  to 
the  gladiolus. 

The  Manubrium  or  first  piece  of  the  sternum  has  an 
anterior  and  posterior  surface,  upper  and  lower  extrem- 
ity and  two  lateral  borders.  The  anterior  surface  is  slightly 
convex  from  Side  to  side,  usually  a  little  concave  from  above 
downward,  and  roughened  for  muscular  attachment.  The 
posterior  is  concave  from  side  to  side  and  smooth.  The  upper 
extremity  is  marked  in  the  mid-line  by  a  notch  known  as  the 
inter-clavicular.  E^xternal  to  this  and  located  at  the  junction 
of  the  upper  extremity  and  lateral  border,  is  a  smooth  con- 
cavo-convex articular  facet  for  the  inner  end  of  the  clavicle. 
This  facet  is  concave  from  above  downward  and  outward  and 
convex  from  before  backward.  The  inferior  extremity  is 
marked  by  an  oval,  oblong  articular  surface  for  the  upper  end 
of  the  Gladiolus.  The  lateral  borders  present  above  a  pit  for 
the  reception  of  the  cartilage  of  the  first  rib  ;  below  a  half 
pit  for  the  second  costal  cartilage,  converted  into  a  whole  pit 
by  articulation  with  the  Gladiolus.  Between  these  the  border 
is  rough,  narrow  and  non-articular. 

The  Gladiolus  or  second  piece  of  the  sternum,  pre- 
sents an  anterior  surface,  slightly  convex  from  above 
downward  and  marked  by  three  transverse  ridges  which 
indicate  the  junction  of  the  four  bones  of  which  it  was 
originally  composed.  The  posterior  surface  is  concave 
and  smooth.  The  upper  extremity  shows  an  oval  articular 
facet  to  correspond  with  the  one  on  the  lower  extremity  of  the 
Manubrium.       The    lower   extremity    shows   a   similar,    but 


OSTEOLOGY.  13 

smaller  facet  for  the  Knsiform  cartilag-e.  The  lateral  borders 
are  marked  by  a  demifacet  at  the  upper  and  lower  ang-les  re- 
spectively and  four  whole  pits  between  these  two.  The  upper 
demifacet  is  for  the  second  costal  cartilag-e,  the  lower,  for 
the  seventh  and  those  between  for  the  cartilag-es  of  the  inter- 
vening" ribs.  Between  these  pits  are  narrow,  roug-h  non- 
articular  portions  of  bone.  Occasionally  the  Gladiolus  shows  a 
foramen  near  its  lower  end. 

The  E^asiform  cartilag-e  presents  many  varieties  in  shape 
and  position.  Above  it  has  a  small  oval  facet  for  the  Gladio- 
lus, and  on  its  lateral  marg-in  a  half  facet  for  the  cartilag-e 
of  the  seventh  rib.  It  is  frequently  deflected  to  one  or  the 
other  side,  and   may  be  turned  backward  or  forward. 

Viewed  as  a  whole  the  Sternum  is  convex  and  roug-h  ante- 
riorly, concave  and  smooth  posteriorly,  larg-e  and  broad  above, 
presenting-  the  articular  facets  for  the  clavicles  and  the  inter- 
clavicular notch,  narrow  and  pointed  inferiorl}^  Laterally  it 
is  marked  by  pits  for  the  reception  of  the  cartilag-es  of  the 
seven  true  ribs. 

The  Ribs. 

The  ribs  are  twelve  pairs  of  long-  bones  situated  on  the  side 
and  front  of  the  chest  and  forming-  the  g-reater  part  of  the  bony 
wall  of  the  thorax.  They  are  known  by  numbers  from  above 
downward.  In  describing-  them  a  rib  from  the  middle  is  taken 
and  the  characteristics  common  to  all  the  ribs  are  described. 
This  is  called  a  typical  rib.  The  peculiar  ribs  are  then 
described.  Of  course  all  the  ribs,  from  any  given  individual, 
may  be  disting-uished,  but  not  from  different  persons. 

A  Typical  Rib. 

A  typical  rib,  being-  a  long-  bone,  has  a  shaft  and  two 
extremities.  The  posterior  or  vertebral  extremity  is  some- 
times improperly  called  the  head.  It  consists  of  a  head,  neck 
and  tubercle.  The  posterior,  or  vertebral  extremity  has  a 
head  which  presents  two  articular  facets  separated  by  an 
antero-posterior  ridg-e.  The  facets  look  the  one  upward  and 
backward,  the  other  downward  and  backward,  are  oval  in  form 
and  articular  for  the  demi-facets  found  on  the  bodies  of  the 


14  DESCRIPTIVE  ANATOMY. 

dorsal  vertebrse  above  and  below.  The  ridg-e  is  received  in 
the  interval  between  the  two  vertebra  and  is  attached  to  the 
intervertebral  disk.  The  neck  extends  outward  and  slig-htly 
backward  from  the  head  and  terminates  at  the  tubercle.  It 
has  an  upper  and  a  lower  border,  anterior  and  posterior  sur- 
faces. The  posterior  surface  is  irreg-ular  and  roug-h  for 
lio-amentous  attachment;  the  anterior,  smooth,  concave,  slopes 
obliquely  from  above  downward  and  enters  into  the  formation 
of  the  posterior  wall  of  the  thorax.  The  lower  border  is 
twice  as  thick  as  the  upper,  is  long-er  and  roughened  for  the 
attachment  of  a  ligament.  The  superior  border  is  marked  by 
a  prominent  crest  which  extends  from  the  head  to  near  the 
tubercle.  In  the  lower  ribs  it  rises  from  behind  forward  and 
terminates  rather  abruptly  before  reaching  the  tubercle  ;  in 
the  upper  it  is  less  prominent  and  might  be  described  as  a 
simple  ridge  marking*  the  upper  border. 

The  anterior,  or  sternal,  extremity,  is  flattened  from  before 
backwards,  slig-htly  larg-er  than  the  shaft  and  is  surmounted 
bv  a  pit  for  the  reception  of  the  corresponding-  costal  cartilag-e. 

The  shaft  slopes  obliquely  from  above  downward  and  for- 
ward, the  degree  of  obliquity  varying  with  the  different  ribs. 
It  presents  two  surfaces,  internal  and  external,  and  two  bor- 
ders, inferior  and  superior.  The  posterior  part  of  the  shaft 
is  nearly  round  and  extends  from  the  tubercle  to  the  ang-le  of 
the  rib.  Its  surfaces  look  forward  and  backward.  Prom  the 
angle  the  ribs  slope  and  the  surfaces  become  internal  and  ex- 
ternal. The  external  surface  is  convex  from  before  backward, 
flat  or  slightly  convex  from  above  downward  and  is  marked  at 
the  angle  of  the  bone  by  an  oblique  ridge.  The  internal  sur- 
face is  concave  from  before  backward,  convex  from  above 
downward  and  smooth.  Near  the  lower  border  is  seen  a  long- 
g-roove  which,  starting  near  the  angle  passes  forward  to  the 
anterior  third  where  it  gradually  loses  itself  on  the  inferior 
border.  The  superior  border  is  twice  as  thick  as  the  inferior 
and  is  slig-htly  roug-hened  for  muscular  attachment.  The  in- 
ferior border,  thin  and  sharp,  overhangs  the  g-roove  on  the 
inner  surface  and  is  itself  marked  by  the  same  g-roove  near  its 
anterior  extremit}'. 


OSTEOLOGY.  15 

Peculiar  Ribs. 

The  peculiar  ribs  are  the  first,  second,  tenth,  eleventh,  and 
twelfth. 

The  First  Rib  departs  more  widely  from  the  t3'pical  rib 
than  any  other.  Its  surfaces  look  one  upward  and  forward, 
the  other  downward  and  backw^ard,  its  borders  inward  and 
outward. 

The  superior  surface,  broad  and  fiat,  presents  near  the 
middle  an  oblique  ridg-e  which  separates  two  g^rooves,  the  in- 
ternal for  the  subclavian  vein,  the  external  for  the  subclavian 
artery.  The  external  border,  convex  and  roug-h  and  thicker 
than  the  internal  border,  is  not  marked  by  either  ang-le  or 
ridge  as  is  the  case  with  a  typical  rib.  The  posterior  extrem- 
ity presents  a  head  with  only  one  articular  facet,  as  this  rib 
articulates  with  but  one  vertebra.  The  neck  is  flattened 
from  above  downward  and  has  no  crest.  The  anterior  ex- 
tremity is  thick  and  roug-h,  being*  marked  on  its  upper  sur- 
face by  a  roug-h  elevation  for  the  attachment  of  a  lig-ament. 
The  inferior  surface  is  smooth. 

The  second  rib,  long-er  than  the  first,  approaches 
more  nearly  the  typical  rib.  It  is  marked  by  a  crest  on 
its  neck  and  an  ang-le  and  ridg-e  on  the  shaft,  but  both 
are  less  distinct  than  in  the  typical  rib.  The  tenth, 
eleventh,  and  twelfth  each  have  a  whole  facet,  articu- 
lating- with  but  a  single  vertebra.  The  tenth  has  a  pit  at  its 
chondral  extremity  for  the  reception  of  a  cartilage  which  binds 
it  to  the  cartilag-e  of  the  ninth  and,  throug-h  it,  to  the  seventh. 
The  eleventh  and  twelfth  are  merely  tipped  at  their  extrem- 
ity with  cartilag-e  and  are  called  floating-  ribs,  because  they 
are  not  attached  to  any  other  rib.  These  ribs  have  no  artic- 
ular facet  on  the  tuberosity  for  the  transverse  process. 

The  Costal  Cartilages. 

The  costal  cartilag-es  are  flat  pieces  of  hyaline  cartilag-e 
attached  by  one  extremity  to  the  ribs  and  by  the  other  to  the 
pits  on  the  lateral  aspect  of  the  sternum.  Their  surfaces  are 
anterior  and  posterior  and  the  borders  superior  and  inferior. 


16  DESCRIPTIVE  ANATOMY. 

They  increase  in  leng"th  from  the  first  to  the  seventh  and 
each  has  its  separate  pit  on  the  sternum  down  to  and  includino- 
the  seventh.  From  the  seventh  the  cartilages  are  attached  to 
the  cartilag-e  of  the  seventh  rib  and  through  it  to  the  ster- 
num. It  is  from  this  arrangement  of  the  cartilages  that  the 
upper  seven  ribs  are  called  vertebro-sternal,  the  next  three, 
vertebro-chondral  and  the  last  two  vertebral.  The  first 
three  cartilages  are  horizontal,  the  next  seven  inclined  ob- 
liquely upward,  the  obliquity  increasing  from  the  fourth  to 
the  tenth,  while  the  last  two  are  horizontal  or  inclined 
slightly  downward. 

The  Clavicle. 

The  Clavicle  or,  collar-bone,  extends  nearly  horizon-- 
tally  outward  but  inclined  slightly  upward,  from  the  upper 
end  of  the  sternum  on'  either  side.  It  is  a  long  bone  ;  and 
like  other  long  bones,  is  divided  for  study  into  a  shaft  and 
two  extremities.  The  inner  extremity  is  thick,  the  bone  grad- 
ually diminishing  in  size  as  it  passes  from  the  inner  to  the 
outer  end.  The  bone  is  round  or  triangular  ;  and  bears  on  its 
inner  extremity  a  concavo-convex  articular  surface,  convex 
from  above  downward  and  outward,  concave  from  before  back- 
ward. This  surface  is  intended  for  articulation  with  a  simi- 
lar saddle-shaped  surface  on  the  upper  outer  aspect  of  the  first 
piece  of  the  sternum.  Generally,  just  below  this,  is  found 
another  articular  facet  to  play  upon  the  cartilage  of  the  first 
rib.  The  outer  extremity  is  flattened  from  above  downward, 
rough  and  subcutaneous  on  its  upper  surface,  slightly  rough- 
ened on  its  lower  surface,  and  presents  at  its  tip  a  small  articu- 
lar facet,  oval  in  outline,  the  long  diameter  directed  from  be- 
fore backward,  and  looking  downward  and  outward.  This 
is  for  articulation  with  the  the  acromion  process  of  the  scapula. 
The  body  of  the  bone  presents  two  surfaces,  superior  and 
inferior  ;  and  two  borders,  anterior  and  posterior. 

The  inferior  surface  presents  a  long  shallow  groove,  the 
subclavian,  terminated  internally  by  the  roughened  surface 
which  is  sometimes  a  process  and  sometimes  a  depression, 
called   the    rhomboid    impression.      Following    the    groove 


OSTEOLOGY.  17 

outward,  we  reach,  near  the  posterior  border  of  the  bone, 
a  prominent  tubercle,  called  the  conoid ;  and  extending* 
outward  and  forward  from  this  is  a  roug-hened  ridg-e, 
called  the  trapezoid  ridg-c.  The  superior  surface  is  round, 
convex,  smooth  except  at  its  inner  and  outer  ends, 
where  it  is  roughened  for  muscular  attachment,  and  is 
subcutaneous.  The  aulerior  border  is  convex  for  its  inner 
two-thirds,  thick  and  round;  concave  for  its  outer  one-third, 
thin  and  sharp.  The  posterior  border  is  concave  for  its  inner 
four-fifths,  and  is  smooth  ;  it  is  convex  for  its  outer  one-fifth, 
and  is  rough,  thicker  than  the  outer  part  of  the  anterior  bor- 
der, but  not  so  thick  as  the  inner  extremity  of  the  posterior 
border  itself.  The  upper  surface  and  anterior  border  are 
subcutaneous. 

The  Scapula. 

The  scapula,  or  shoulder  blade,  is  a  flat  triangular  bone, 
situated  on  the  upper  postero-lateral  aspect  of  the  chest, 
extending"  over  the  upper  eig-ht  ribs  with  the  exception  of  the 
first.  It  consists  of  a  body  having-  two  surfaces  and  three 
borders,  three  angles  and  two  processes. 

The  anterior  face,  or  venter,  is  concave,  has  ridg-es  run- 
ning- upward  and  outward,  and  presents  a  deep  depression 
towards  its  upper  outer  part,  which  is  called  the  subscapular 
angle.  This  face  of  the  scapula  is  in  the  main  occupied  by 
the  subscapular  fossa;  but  it  must  be  remembered  that  there 
is  a  smooth  surface  at  the  superior  and  inferior  angles  of  the 
bone  and  along  the  posterior  border,  which  while  belonging- 
to  the'venter  of  the  scapula,  does  not  belong-  to  the  subscapular 
fossa. 

The  posterior  face,  or  dorsum,  is  convex  from  above 
downward,  presenting-  a  prominent  ridg-e,  the  spine,  which 
commences  at  the  posterior  border  and  runs  upward  and  out- 
ward towards  the  head,  dividing-  the  dorsum  into  two  unequal 
parts  :  the  smaller  above  called  the  supraspinous  fossa,  and  the 
three-fold  larger  below  called  the  infraspinous  fossa. 

The  supraspinous  fossa  is  triangular  in  outline,  the  apex 
of  the  triang-le  being-  directed  outward,  is  concave  from  above 
downward  and  from  before  backward,  and  smooth. 


18  DESCRIPTIVE  ANATOMY. 

The  iufraspinous  fossa  occupies  nearly  all  of  the  remaining- 
portion  of  the  dorsum  of  the  scapula  ;  but  there  is  a  strip  along" 
the  anterior,  or  axillary,  border,  and  a  triang-ular  space  at  the 
inferior  angle  which  do  not  belong  to  the  infraspinous  fossa, 
thoug^h  they  belong-  to  the  dorsum  of  the  scapula.  The  fossa, 
which  is  triangular  in  outline,  the  apex  directed  downward 
and  the  base  upward,  presents  near  its  center  a  prominent 
bulg-e,  and  external  to  this  a  broad  vertical  g-roove.  External 
to  this  groove  is  a  prominent  ridg-e  which  extends  as  far  as  the 
axillary  border  of  the  scapula.  It  is  useless  to  say  that  the 
spine  furnishes  a  portion  of  both  supra  and  infraspinous  fossse. 

The  sj^ine  is  triang-ular  and  presents  three  borders,  two 
of  which  are  free,  one  looking-  backward  and  the  other  outward 
and  forward.  The  one  which  looks  directly  forward,  the  so-' 
called  "attached  border,"  is  simply  the  attachment  of  the  spine 
to  the  remaining-  portion  of  the  bone.  The  spine  itself  presents 
a  superior  surface  which  is  concave,  and  enters  into  the  for- 
mation of  the  supraspinous  fossa,  and  an  inferior  surface 
which  is  slig-htly  convex  from  without  inward,  slightly  concave 
from  above  downward,  smooth,  and  forms  part  of  the  infra- 
spinous fossa.  Its  posterior  border  is  roug-h,  commences  as  a 
smooth  triang-ular  surface  near  the  vertebral  border  of  the 
bone,  rises  as  it  passes  forward  becomes  thicker  and  rougher, 
and  terminates  near  the  upper  outer  angle  by  becoming-  a 
roughened  projection  of  bone,  known  as  the  acromion  process. 

This  posterior  border  presents  a  superior  lip,  an  inferior 
lip,  and  an  intermediate  space  intended  for  muscular  attach- 
ments. 

The  external  border  of  the  spine  is  smooth,  round,  and  con- 
cave, and  is  the  inner  limit  of  the  g-roove  which  extends  around  it 
and  forms  the  means  of  communication  between  the  supra  and 
infraspinous  fossae.  The  superior  border  of  the  scapula  is 
thin,  and  is  the  shortest  of  the  borders.  Near  its  outer  ex- 
tremity it  is  deeply  notched,  the  notch  being  known  as  the 
suprascapular  notch. 

It  terminates  in  the  superior  ang-le  of  the  bone  by  joining 
with  the  posterior  or  vertebral  border. 


OSTEOLOGY.  19 

The  posertior  or  vertebral  border,  commencing-  at  the  supe- 
rior angle  passes  downward  and  inward  to  the  point  at  which 
the  spine  spring-s  from  the  posterior  border.  Prom  this  point 
downward  it  chang-es  its  direction,  and  is  nearly  vertical,  with 
a  slig-ht  inclination  outward.  This  border  of  the  scapula,  like 
the  posterior  border  of  the  spine,  is  composed  of  two  lips  and 
a  roug"h  intervening*  space.  It  is  intermediate  in  thickness  be- 
tween the  superior  and  the  axillary  borders. 

The  a?iterior,  or  axillary,  or  outer  border  is  thick.  Just  be- 
low the  external  ang-leof  the  bone  it  presents  a  roug-h  impress- 
ion from  one-half  to  three-quarters  of  an  inch  in  leng-th,  which 
is  intended  for  muscular  attachment.  Below  this  point  is  seen 
a  vertical  g-roove,  which  passing-  downward  upon  the  axillary 
border  winds  g-radually  to  the  posterior  surface  of  the  bone, 
which  it  reaches  at  the  junction  of  the  lower  third  with  the 
upper  two-thirds  of  the  axillary  border.  Starting  from  the 
rough  impression  is  a  vertical  ridg-e,  which  is  the  posterior 
boundary  of  the  above-mentioned  groove.  Crossing  this  ridge 
at  the  middle  of  the  axillary  border  of  the  scapula  is  a  trans- 
verse groove  which  transmits  an  artery  from  the  anterior  to 
the  posterior  surface  of  the  scapula.  Below  the  termination  of 
the  vertical  groove  the  axillary  border  of  the  scapula  becomes 
thinner,  and  is  roughened  for   muscular  attachment. 

Of  the  angles  of  the  bone  the  superior  is  situated  at  the 
junction  of  the  superior  and  posterior  borders,  and  is  about  a 
right  angle.  It  is  usually  deflected  slightly  backward  ;  and 
presents  anteriorly  a  smooth  surface,  belonging  to  the  venter 
of  the  scapula,  but  not  entering  into  the  subscapular  fossa. 

The  inferior  angle  at  the  junction  of  the  posterior  and  axil- 
lary borders  is  acute,  having  a  roughened  surface  anteriorly 
and  posteriorly.  The  anterior  angle  is  expanded,  and  is  the 
thickest  portion  of  the  bone.  It  is  frequently  called  the 
"head"  of  the  bone  ;  and  bears  upon  its  extremity  a  hollow, 
oblong,  vertical  concavity,  known  as  the  glenoid  cavity. 
This  cavity  has  its  long  diameter  directed  from  above 
downward.  It  is  oval  in  outline,  with  the  large  end  below 
and  the  small  end  above.     It  is  supported   upon  the  bone  by 


20  DESCRIPTIVE  ANATOMY. 

the  narrow  constricted  portion,  which  is  called  the  "neck"  of 
the  scapula. 

This  neck  is  distinct  anteriorly  and  posteriorly  ;  but  above  is 
obscured  by  the  orig-in  of  the  coracoid  process  of  the  bone, 
and  below  by  the  impression  for  the  attachment  of  the  triceps 
muscle. 

The  processes  are  two :  the  coracoid  process,  which 
spring's  from  the  bone  just  above  the  glenoid  cavity.  Its  direc- 
tion is  at  first  upward  and  slig^htly  forward,  but  after  pass- 
ing a  short  distance,  about  half-an-inch,  it  abruptly  changes 
its  course,  and  runs  nearly  outward,  with  a  slight  inclination 
forward.  At  its  origin  one  surface  looks  upward  and  back- 
ward and  the  other  downward  and  forward  ;  but  after  the 
change  in  its  direction  one  surface  looks  upward  and  forward 
and  the  other  one  downward  and  backward.  The  upper 
surface  is  roughened  for  muscular  attachment,  while  the 
lower  is  smooth  and  concave.  The  tip  is  marked  by  a  smooth 
impression  for  muscular  attachment. 

The  Acromion  Process,  is  the  termination  of  the  spine. 
It  presents  one  surface  which  looks  upward  and  back- 
ward, one  which  looks  downward  and  forward,  an  external 
border,  an  internal  border,  and  an  apex.  The  superior  sur- 
face is  rough,  irregular  and  subcutaneous  ;  the  inferior  surface 
is  rather  smooth,  is  concave,  and  is  pierced  by  numerous 
nutrient  foramina.  The  external  border  is  convex  and  roug'h 
for  muscular  attachment.  The  internal  border  is  concave  ; 
and  is  marked  near  its  outer  extremity  by  a  smooth,  oblong- 
articular  facet,  the  long-  diameter  of  which  extends  from  be- 
fore backward  ;  and  the  surface  itself  is  oblique,  looking* 
slightly  upward  and  inward.  The  apex  is  roughened  for 
muscular  attachment.  The  upper  surface  of  this  process  ap- 
pears to  be  a  continuation  of  the  posterior  border  of  the  spine, 
whose  superior  lip  corresponds  to  the  inner  border  of  the 
process,  the  low^er  lip  to  the  outer  border,  while  the  rough 
intermediate  lip  expands  into  the  upper  surface. 

The  Humerus. 

The  Humerus,  (L.  Humerus)  or  skeleton  of  the  upper  ex- 
tremity, is  a  long-  bone  having  a  shaft  and  two  extremities. 


OSTEOLOGY.  21 

The  Head,  or  Upper  Extremity,  presents  for  examina- 
tion a  smooth,  rounded  portion  the  head  proper,  form- 
ing- something-  less  than  half  a  sphere,  which  looks  up- 
ward, inward  and  backward  and  is  articular  for  the 
glenoid  cavity  of  the  Scapula.  E^xternal  to  this  is  a 
constricted  part  of  the  bone,  separating-  the  head  from  the 
next  appearances,  called  the  anatomical  neck.  It  is  narrow 
and  well  marked  above  but  becomes  indistinct  below  and  be- 
hind. External  to  the  anatomical  neck  there  is  a  largfe  projec- 
tion called  the  g^reater  tuberosity.  It  is  prominent  and  bulg-- 
ing,  looks  outward  and  forward  and  has  on  its  summit  three 
smooth  impressions  for  the  attachment  of  three  of  the  muscles 
of  the  scapular  g-roup.  Internal  to  the  greater  is  a  smaller 
projection  called  the  lesser  tuberosity.  It  is  sharper  and 
more  prominent  than  the  greater  tuberosity  and  has  on  its 
summit  but  one  muscular  impression.  Between  the  two  tuber- 
osities is  a  deep  groove,  the  bicipital,  bounded  on  either  side 
by  two  prominent  ridges,  the  internal  and  external  bicipital 
ridges  of  the  humerus.  Below  the  tuberosities  the  bone  is 
constricted  and  round,  forming  the  surgical  neck. 

The  Louver  Extremity  is  flattened  from  before  backward,  is 
bent  forward,  and  presents  a3light  curve  of  torsion  from  with- 
out inward.  On  either  side  is  a  rough  prominence  called,  im- 
properly, the  condyle,  internal  and  external,  the  internal  being 
the  larger  of  the  two.  From  either  condyle  there  passes  up 
to  the  shaft  of  the  bone  a  large  ridge  of  which  the  external  is 
much  more  prominent  and  curved  than  the  internal.  Proceed- 
ing now  from  the  external  condyle  inward,  we  next  see  a 
rounded  articular  surface,  the  eminentia  capitata,  whose 
articular  surface  extends  higher  up  anteriorly  than  posteriorly. 
It  is  for  articulation  with  the  cup-like  cavity  on  the  upper  ex- 
tremity of  the  radius.  Internal  to  this  is  a  shallow  articular 
groove  for  the  play  of  the  rim  around  the  head  of  the  radius. 
Internal  to  this  we  encounter  two  antero-posterior  articular 
ridges,  separated  by  an  antero-posterior  articular  groove  the 
three  forming  a  trochlear  surface  for  the  reception  of  the 
greater   Sigmoid   cavity  of  the   Ulna.     The  internal   ridge  is 


22  DESCRIPTIVE  ANATOMY. 

larger  and  its  articular  surface  extends  higher  up  in  front 
than  the  external.  Above  the  trochlea,  both  before  and  be- 
hind, is  a  deep  pit-like  depression.  The  one  in  front  is  for 
the  reception  of  the  coronoid  process  of  the  Ulna,  the  one  be- 
hind for  the  Olecranon.  The  olecranon  fossa  is  deeper  and 
larger  than  the  coronoid.  In  some  bones,  the  thin  septum 
separating  the  two  cavities  is  absent  and  then  there  is  a  fora- 
men between  the  two  fossae.  Between  the  inner  condyle  and 
the  internal  surface  of  the  trochlea,  is  a  deep  depression  for 
the  passage  of  an  important  nerve. 

The  Shaft  of  the  bone,  cylindrical  above,  prismoid  in  the 
middle  and  below,  presents  three  surfaces  and  three  borders. 
The  borders  are  anterior  and  two  lateral;  the  surfaces,  poste- 
rior and  two  lateral. 

The  anterior  border  begins  at  the  greater  tuberosity  as  the 
external,  or  anterior  bicipital  ridge.  Prominent  and  well 
marked  above,  it  passes  down  the  mid-line  of  the  bone  to  termi- 
ate  at  the  coronoid  fossa,  separating  the  internal  from  the 
external  surface.  The  internal  border  begins  above  as  the 
inner  bicipital  ridge.  It  passes  at  first  downward  and  back- 
ward, then  vertically  downward  to  terminate  as  the  internal 
condyloid  ridge.  It  is  prominent  above  and  below,  less  dis- 
tinct in  the  middle  of  its  course.  The  external  border  com- 
mences at  the  back  of  the  greater  tuberosity  and  passes  straight 
down  to  the  outer  condyle  where  it  becomes  the  external  condy- 
loid ridge.  "Very  sharp  and  prominent  below,  rough  and  well 
marked  above,  it  is  obliterated  in  the  middle  by  the  passage  of 
the  musculo-spiral  groove. 

The  internal  surface  begins  as  the  bottom  of  the  bicipital 
groove.  It  passes  downward  and  backward  at  first  and  then 
vertically  downward.  It  is  narrow  above,  wider  in  the  mid- 
dle and  smooth  and  looking  forward  and  inward  below.  This 
surface  is  usually  marked  about  its  middle  by  the  nutrient 
foramen,  though  this  appearance  is  often  found  on  the  inner 
border. 

The  external  surface  begins  at  the  base  of  the  greater 
tuberosity,  passes  straight  downward  to  the    middle   of  the 


OSTEOLOGY.  23 

bone  and  then  curves  forward  until  it  is  almost  anterior. 
About  the  middle  of  this  surface  there  is  a  larg-e  roug-h  surface, 
with  the  apex  downward,  called  the  deltoid  impression  from 
its  supposed  resemblance  to  the  Greek  "Delta"  inverted.  Be- 
low the  apex  of  the  impression  the  musculo-spiral  groove 
crosses  to  the  front,  smoothing  the  outer  face,  which  remains 
smooth  and  without  appearances  throughout.  The  posterior 
face  is  round  and  smooth  above,  but  becomes  broad  and  flat 
below.  Commencing  on  the  posterior  surface  and  winding 
downward  and  outward, is  a  broad  shallow  groove, the  musculo- 
spiral.  This  groove  is  indistinct  on  the  posterior  face,  obliter- 
ates about  two  inches  of  the  outer  border  and  is  finally  lost  on 
the  external  face. 

The  Ulna. 

The  Ulna  is  a  long  bone,  consisting  of  a  shaft  and  two  ex- 
tremities, distinguished  as  upper  and  lower.  It  is  the  inner 
and  more  massive  of  the  bones  of  the  fore-arm. 

The  Upper  Extremity  is  composed  of  two  processes  called 
olecranon  and  coronoid.  The  olecranon  process  is  found  oc- 
cupying the  summit  of  the  bone  and  may  itself  be  divided  for 
study  into  a  superior,  posterior  and  anterior  surface  and  two 
lateral  borders.  The  upper  surface,  indistinctly  quadrilateral 
in  outline,  terminates  anteriorly  in  a  bluntly  pointed  projection 
called  the  beak,  and  is  marked  by  a  rough  surface  posteriorly 
for  the  attachment  of  a  muscle,  while  in  front  is  found  a 
transverse  groove  extending  backward  to  become  continuous 
with  grooves  which  mark  the  lateral  borders.  The  posterior 
surface  is  triangular  in  form,  the  large  end  of  the  triangle 
directed  upward,  rough  and  subcutaneous.  The  anterior  sur- 
face is  concave  from  above  downward,  convex  from  side  to 
side,  articular  and  enters  into  the  formation  of  the  greater 
sigmoid  cavity. 

The  Coronoid  process  juts  forward  from  the  front  of  the 
bone.  It  is  triangular  in  form,  the  base  of  the  triangle  being 
attached  to  the  bone  while  the  apex  points  forward.  It  pre- 
sents a  superior  and  an  inferior  surface  and  two  lateral  margins. 
The  superior  surface  is  smooth  and  articular,  convex  from 


24  DESCRIPTIVE  ANATOMY. 

side  to  side,  concave  from  before  backward,  and  is  continuous 
with  tHe  similar  surface  on  the  olecranon  process.  The  infe- 
rior surface  is  very  irregular.  It  is  marked  near  its  middle 
by  a  rough  impression  for  the  attachment  of  a  muscle,  the 
brachialis  anticus  ;  at  its  junction  with  the  shaft,  usually,  by 
a  slight  projection,  the  tubercle  of  the  ulna,  and  at  its  junc- 
tion with  the  internal  margin  by  a  roughened  elevation,  also 
for  muscular  attachment.  The  inner  margin  is  roughened  for 
muscular  attachment ;  the  external  presents  a  concave,  oval, 
articular  facet,  the  long  diameter  from  before  backward,  which 
receives  the  rim  around  the  head  of  the  radius.  It  is  called 
the  Lesser  Sigmoid  cavity  of  the  ulna.  The  Greater  Sigmoid 
cavity  is  formed  by  the  two  processes,  is  concave  from  above 
downward,  convex  from  side  to  side  and  might  be  described 
as  consisting  of  four  depressions,  two  on  either  process,  to 
receive  the  articular  ridges  on  the  Humerus,  separated  by  a 
vertical  ridge  and  a  transverse  groove.  The  outer  side  of  this 
cavity  is  continuous  with  the  Lesser  Sigmoid  cavity. 

The  Lozver  Extrejnity  of  the  ulna  is  much  smaller  than  the 
upper,  and  consists  of  two  projections  separated  by  a  notch, 
the  inner  on  the  postero-internal  aspect  of  the  bone  is  the 
smaller  and  longer,  and  terminates  in  a  blunt  point.  It  is 
called  th.e.  styloid  ■p7'ocess  of  the  ulna.  The  outer  process  is 
called  the  capitiiliim  2el?2ce(Dim..  of  Latin  caf>i{t,  head)  and  is 
artfcular  upon  its  summit  and  around  the  greater  portion  of  its 
circumference.  The  notch  which  separates  the  two  processes 
is  narrow,  and  is  intended  for  the  attachment  of  the  fibro- 
cartilage  which  enters  into  the  formation  of  the  wrist  joint. 
The  articular  surface  upon  the  summit  is  smooth,  slightly 
concave,  and  does  not  directly  articulate  with  the  carpus  but 
only  through  the  interposition  of  the  fibro-cartilage.  The 
articular  rim  which  surrounds  three-fourths  of  its  circumfer- 
ence is  smooth  and  convex,  and  intended  to  play  in  the  cavity 
which  is  found  upon  the  lower  extremity  of  the  radius. 

The  Shaft  of  the  ulna  is  distinctly  three-sided  ;  and  hence 
presents  three  borders  and  three  surfaces.  The  surfaces  are 
anterior,   internal  and   posterior  ;  the   borders   are   anterior, 


OSTEOLOGY.  25 

posterior  and  external,  or  interosseous.  The  anterior  surface 
is  broad  above,  narrow  and  round  below.  For  the  upper 
three-fourths  of  its  course  it  is  usually  concave  from  side  to 
side,  presenting-  a  shallow  groove.  The  subcutaneous  inter- 
nal surface  is  broadband  flattened  above,  convex  and  slightly 
flattened  in  the  middle,  round  and  narrow  below.  The  poste- 
rior surface  is  widest  about  its  middle  and  presents  usually  a 
vertical  ridge,  which  divides  it  into  two  unequal  portions,  of 
which  the  inner  part  is  the  broader.  The  upper  portion  of 
this  surface  presents  a  small  triang'ular  space ;  below  it  is 
rounded  like  the  remaining  surfaces.  Of  the  borders,  the 
anterior  begins  above  at  the  inner  side  of  the  base  of  the  coro- 
noid  process.  Prominent  and  well-marked  above,  it  passes 
downward  to  the  front  of  the  styloid  process,  becoming  rounder 
and  more  indistinct  in  the  lower  one-third  of  its  course.  The 
posteterior  border  commences  above  at  the  apex  of  the  triangle 
of  the  posterior  surface  of  the  oelcranon  process.  Prominent, 
well-marked,  and  sub-cutaneous  above,  it  becomes  round  and 
smooth  below,  and  terminates  at  the  back  of  the  styloid  pro- 
cess. The  external  or  interosseous  border  commences  by  the 
convergence  of  two  lines,  one  from  either  side  of  the  lesser 
sigmoid  cavity.  It  is  sharp,  thin,  and  well-marked  for  the 
middle  two-fourths  of  its  course.  Below  it  becomes  indistinct 
or  imperceptible,  and  terminates  at  the  front  of  the  capitulum 
ulnai. 

The  Radius. 

The  Radius  (L.  radius,  a  ray,  or  spoke  of  a  wheel)  is  the 
outer  of  the  two  bones  of  the  fore-arm  ;  and  like  other  long 
bones  it  is  divided  into  a  shaft  and  two  extremities. 

Its  Ufiper  Extremity,  unlike  the  ulna,  is  much  smaller  than 
its  lower  ;  and  presents  for  examination  a  head  upon  whose 
summit  is  an  articular,  cup-shaped  depression  for  articulation 
with  the  eminentia  capitata  of  the  humerus.  This  depression 
is  surrounded  by  an  articular  rim  ;  and  is  supported  upon  a 
constricted  portion  called  the  "neck,"  which  terminates  below 
on  its  inner  aspect  in  a  prominent  projection,  called  the  tuber- 
cle  or    bicipital    tuberosity   of    the    radius.     This    tuberosity 


26  DESCRIPTIVE  ANATONY. 

presents  posteriorly  a  prominent  roug-h  elevation,  for  mus- 
cular attachment  while  anteriorly  it  has  a  smooth  surface 
for  the  play  of  a  bursa. 

On  the  large  Lozuer  Extrejuity  we  find  the  summit  present- 
ing- a  triangular  articular  cavity,  the  carpal,  with  its  apex 
directed  outward,  and  terminating-  in  a  point  or  projection, 
called  the  styloid  process.  The  base  is  directed  inward,  and 
is  continuous  with  the  articular  facet  found  on  the  inner  aspect 
of  the  lower  extremity.  The  carpal  cavity  is  divided  into  two 
portions  by  a  slig"ht  antero-posterior  ridge.  The  external 
portion  is  continued  from  the  summit  of  the  bone  on  to  the 
inner  face  of  the  styloid  process  ;  and  is  triang*ular  in  form. 
The  internal  portion,  quadrilateral  in  form,  is  continuous  with 
the  smooth  oval,  oblong*  articular  facet,  whose  long*  diameter 
is  directed  from  before  backward,  found  on  the  inner  face  of 
the  lower  extremity,  and  called  the  sig'moid  cavity  of  the 
radius.  Between  these  two,  the  sigmoid  and  carpal  cavities, 
is  found  a  non-articular  strip,  intended  for  the  attachment 
of  the  fibro-cartilage.  The  anterior  face  of  the  lower  ex- 
tremity is  roug-h,  and  projects  forward. 

The  posterior  face  is  rough  and  irregular.     It  is  marked  by 

^  five  vertical  grooves  with  intervening  ridges.  Two  of  these 
grooves  are  found  upon  the  styloid  process,  while  of  the 
remaining  three,  one,  very  narrow,  is  separated  from  the 
styloid  process,  b}''  a  very  prominent  projection  of  the  bone, 
while  the  other  is  broad  and  shallow,  and  is  found  near  the 
inner  end  of  the  posterior  face. 

The  Styloid  Process  itself  presents  an  internal  and  an  exter- 
nal face  :  the  internal  being  articular,  and  continuous  with  the 

8  articular  surface  of  the  carpal  cavity  ;  the  external  rough  for 
ligamentous  attachment,  and  marked  by  the  grooves  above 
mentioned.  Its  anterior  and  posterior  borders  are  roughened, 
while  its  tip  has  a  blunt  point. 

The  Shaft  of  the  radius  has  three  surfaces  and  three  bor- 
ders. The  surfaces  are  anterior,  posterior,  and  external  ; 
the  borders  anterior,  posterior,  and  internal  or  interosseous. 
The  anterior  face  is  narrow  above,   slightly  convex,  becomes 


OSTEOLOGY.  27 

broader  as  It  approaches  the  lower  extremity  of  the  bone, 
is  slig-htly  concave  in  the  middle  and  is  flat  at  the  lower 
end.  It  is  marked  b}^  an  oblique  ridg-e,  which  will 
be  mentioned  later.  The  -posterior  face  is  convex  in  the 
upper  and  lower  portions  of  its  course,  slightly  concave 
in  the  middle.  The  external  face  is  convex  throughout 
its  extent,  so  that  the  bone  appears  to  be  bowed  outward. 
The  anterior  border  begins  at  the  front  of  the  bicipital  tuber- 
osity ;  it  passes  downward  and  outward,  crossing-  the  upper 
one-third  of  the  bone  until  it  reaches  its  middle  third,  in 
which  situation  it  is  known  as  the  oblique  line  of  the  radius 
mentioned  above. 

From  this  point  it  continues  vertically  downward  to  the 
front  of  the  styloid  process  of  the  radius,  where  it  terminates. 
The  posterior  border  beg"ins  at  the  back  of  the  neck  of  the 
radius,  and  running-  vertically  downward,  more  prominent  in 
the  middle  than  elsewhere,  terminates  at  the  back  of  the  sty- 
loid process.  The  internal  border  or  interosseous  ridg-e, 
beg-ins  also  at  the  tuberosity  near  its  posterior  portion,  passes 
downward,  sharp  and  prominent  about  its  middle,  more  indis- 
tinct below,  and  terminates  at  the  lower  extremity  of  the 
bone,  by  dividing-  into  two  lines  which  enclose  the  sigmoid 
cavity  of  the  radius. 

The  Hand. 

The  skeleton  of  the  hand  consists  of  the  skeleton  of  the 
Carpus,  the  Metacarpus,  and  Phalanges. 

The  Carpus. 

The  skeleton  of  the  carpus  or  wrist,  consists  of  seven  small, 
irregular  bones,  arranged  in  two  rows  one  above  the  other  ; 
in  the  upper  row  are  three  bones,  arranged  in  the  following 
order  from  without  inward:  1st,  the  Scaphoid;  2nd,  the 
Semilnnar  ;  3d,  the  Cuneiform,  on  the  front  of  which  plays  a 
sesamoid  bone,  called  the  Pisiform.  In  the  lower  row  in  the 
same  order  are  :  1st,  the  Tra-pcziiim  ;  2nd,  the  Trapezoid  \  3d, 
the  Os  Magnum  ;  4th,  the  Unciform. 

The  Bones  of  the  Upper  Row. 

The   bones  of  the   upper   row  articulate  laterally  with  one 


28  DESCRIPTIVE  ANATOMY. 

another  ;  the  bones  on  the  inner  and  outer  side  respectively 
have  no  bones  on  the  inner  side  of  the  one  and  the  outer  side 
of  the  other,  and  hence  there  is  no  articular  surface  on  that 
aspect  of  the  bones.  It  must  be  further  noted  that  viewed 
from  the  back  there  appear  to  be  but  three  bones  in  the  upper 
row,  placed  laterally,  the  scaphoid,  semilunar  and  cueniform  ; 
but  viewed  from  the  front  the  pisiform  is  seen  perched  upon 
the  cuneiform,  so  that  the  latter  bone  has  no  articular  facet  on 
its  inner  side. 

The  Scaphoid.  This  bone  has  a  su-perior  surface,  which  is 
rounded,  convex,  and  articular  for  lower  end  of  Radius;  an 
inferior  surface,  which  is  concave  and  articular  for  the  upper 
extremity  of  the  os  magnum;  an  outer  extremity,  which  looks 
downward  and  outward  and  is  articular  for  the  trapezium 
and  trapezoid;  an  inner  extremity  with  an  oval  articular  facet, 
whose  long  diameter  is  directed  from  before  backward,  for 
articulation  with  a  similar  facet  upon  the  semilunar.  Ivike  all 
the  bones  of  the  carpus,  the  anterior  and  posterior  surfaces  are 
non-articular;  but  unlike  most  carpal  bones,  the  anterior  sur- 
face is  broader  than  the  posterior. 

The  Semilunar,  the  second  bone  in  the  first  row,  has  a  superior 
sinface,  convex,  smooth,  and  articular  for  lower  end  of  Radius; 
an  inferior  surface  having-  two  articular  facets,  one  concave, 
oval,  with  its  long-  diameter  antero-posterior,  articular  for  the 
head  of  the  os  mag-num,the  other  long*  and  narrow  for  the  unci- 
form; an  outer  edg-e,  articular  for  the  scaphoid;  and  an  inner ^ 
triang-ular  in  shape,  larg-er  in  size  than  the  outer  one,  and  ar- 
ticular for  the  cuneiform;  anterior  and  f>osterior  surfaces, 
roug-hened  and  non-articular.  The  anterior  surface  is  broader 
than   the  posterior,  as  is  the  case  with  the  scaphoid. 

The  Cuneiform  presents  an  inferior  surface,  concavo- 
convex  for  articulation  with  the  unciform;  an  external  sur- 
face, flat,  slightly  triang-ular,  articular  for  the  semilunar  ; 
an  antero-external  surface,  which  is  articular  for  the  pisiform, 
while  internally  it  terminates  in  a  blunt  projection  which  is 
not  articular.  Tho.  postei'ior  surface  is  broad  and  roug-h,  the 
anterior  surface  is  rough  and  narrow.     It  is  usually  said  that 


OSTEOLOGY.  29 

this  bone  is  articular  upon  its  anterior  face  ;  but  the  surface 
which  receives  the  pisiform  bone  looks  upward  more  than 
forward,  and  is  also  directed  slig-htly  outward. 

The  Pisiform  is  a  rounded  bone  ;  and  is  in  reality  only  a 
sesamoid  bone,  embraced  by  the  tendon  of  the  flexor  carpi 
ulnaris.  It  is  articular  upon  only  one  surface,  the  surface 
which  looks  downward  and  backward.  It  is  g-enerally  de- 
scribed as  being-  the  only  bone  of  the  carpus  which  is  articular 
upon  its  posterior  surface. 

The  Bones  of  the  Lower  Row. 

The  Trapezium,  the  first  bone  of  the  second  row,  is  easily 
disting-uished  by  the  possession  of  a  concavo-convex,  or  saddle- 
shaped  articular  surface,  which  is  directed  downward  and 
outward.  This  is  its  inferior  surface.  Its  superior  surface 
is  marked  by  a  smooth,  concave  articular  surface  for  the  re- 
ception of  the  outer  end  of  the  scaphoid.  The  outer  surface 
is  roug-h,  prominent  and  non-articnlar.  The  inner  face  is 
marked  above  by  a  smooth  concave  articular  surface  for  the 
outer  face  of  the  trapezoid,  while  below  this,  separated  from 
it  by  a  rough  groove,  is  a  flat  surface,  looking-  downward  and 
inward  for  the  second  metacarpal.  Its  f>osterior  surface, 
broader  than  its  anterior,  is  roug-h  and  prominent,  while  the 
anterior  surface  is  easily  disting-uished  by  an  oblique  g-roove, 
which  runs  from  above  downward  and  inward. 

The  Trapezoid  can  be  most  easily  disting-uished  by  exclusion, 
having-  none  of  the  characteristics  of  the  other  bones.  It  has 
a  broad,  somewhat  quadrilateral  posterior  surface  ;  a  narrow 
and  roug-hened  aiiterior  surface.  Its  superior  surface  is  con- 
cave, and  articular  for  the  held  of  the  scaphoid.  Its  external 
surface  is  slig-htly  convex  above  for  articulation  with  the  trape- 
zium. The  inferior  surface  is  concave  from  before  backward, 
and  articular  for  the  head  of  the  second  metacarpal  bone;  while 
the  internal  surface  is  also  concave  from  before  backward,  and 
articular  for  the  lateral  aspect  of  the  os  magnum. 

The  Os  Magnum  presents  superiorly  a  rounded  articular 
head  to  be  received  in  the  cavity  which  is  furnished  by  the 
scaphoid  and  semilunar  bones,  the  articular  surface  extending 


30  DESCRIPTIVE  ANATOMY. 

further  on  its  posterior  than  on  its  anterior  aspect.  Inferiorly 
it  presents  a  quadrilateral,  oblique  articular  facet,  which  artic- 
ulates with  the  upper  extremity  of  the  third  metacarpal  bone, 
and  which  is  continuous  with  the  articular  facet  found  upon 
its,  inferior  and  external  lateral  aspect  for  the  inner  edg-e  of  the 
upper  extremity  of  the  second  metacarpal  bone.  The  outer 
surface  presents  an  articular  facet,  at  the  anterior  infe- 
rior angle,  convex  from  before  backward,  for  articulation  with 
the  inner  face  of  the  trapezoid.  The  internal  surface  presents 
near  its  posterior  marg-in  an  articular  facet,  broader  above 
than  below  and  somewhat  L-shaped,  the  large  end  of  the  L 
directed  upward.  This  is  for  articulation  with  the  outer  face 
of  the  unciform.  The  -posterior  surface  is  broad,  rough,  and 
marked  by  a  depression  just  below  the  articular  head  ;  the 
anterior  face  ^  narrower,  than  the  posterior,  is  bulging  and 
prominent,  and  roughened  for  ligamentous  attachment. 

The  Unciform  is  more  easily  distinguished  than  any  bone 
of  the  hand.  Its  upper  face  looks  upward  and  inward;  and 
is  frequently  described  as  its  internal  face.  This  face  is  in- 
tended for  articulation  with  the  cuneiform  ;  and  presents  like 
that  bone  a  concavo-convex  articular  surface,  which  is  contin- 
uous with  the  upper  extremity  of  the  bone,  also  convex  for 
articulation  with  the  os  magnum.  Its  outer  face  looks  outward 
and  slightly  downward  ;  and  is  marked  near  the  posterior 
surface  by  an  Iv-shaped  facet,  similar  to  the  one  found  on  the 
inner  surface  of  the  os  magnum,  and  intended  for  articulation 
with  that  bone.  Its  inferior  surface  is  marked  by  two  articu- 
lar facets,  separated  by  a  slight  ridge,  these  facets  articulating 
with  the  fourth  and  fifth  metacarpal  bones.  Its  posterior  face, 
much  broader  than  the  anterior,  is  roughened  for  ligamentous 
attachment.  ^\i^  anterior  face  will  be  at  once  distinguished 
by  a  very  prominent  projection  found  on  the  lower  inner  face 
of  the  bone.  This  projection,  named  the  unciform  p7'ocess, 
looks  forward  and  slightly  outward,  being  a  little  curved  in 
its  course.  It  is  one  of  the  prominent  land-marks  of  the  hand. 
The  remainder  of  the  anterior  face  is  roughened  for  ligamentous 
attachment. 


OSTEOLOGY.  31 

The  Carpus  as  a  xcholc  presents  us  with  four  separate  sets 
of  articulations ;  vi2.  The  articulation  betxveen  the  upper  rozu 
of  the  carpus  and  the  zurist,  the  articulation  between  the  first 
and  second  rows,  the  articulation  between  the  second  row  and  the 
metacarpal  bones,  and  the  articulations  between  the  individual 
bones  of  the  carpus.     When  examined  in  the  articulated  skel- 
eton,   it   is  seen   that  the   superior   row   presents  a  condyle, 
oblong-,  oval  and  articular.     The  long-  diameter  of  this  condyle 
is  transverse  ;  the  bones  which  form  it  are   from   without  in- 
ward :  the  scaphoid,  the  semilunar,  and  the  cuneiform,  the 
pisiform    not  entering-  into    its    formation.      The   articulation 
Ijctzjeoi  the  tzuo  7'ozus  of  carpal  bo)ies  is  sinuous  in  outline,  or 
concavo-convex,  the  trapezium  and  trapezoid  tog-ether  forming- 
a  cavity   for  the  reception   of  the  head  of  the  scaphoid,  while 
the  head  of  the  os  mag-num  and  the  upper  end  of  the  unciform 
form  tog-ether  a  convex  articular  surface  received  into  a  con- 
cavity which  is  contributed  to  by  the  scaphoid,  the  semilunar, 
and  the  cuneiform  bones.      The  articulation  betzveen  the  bo?ies 
of  the  second  roz'j  and  the  metacarpal  bones  consists  first  of  a 
saddle-shaped  articulation,  the  trapezo-metacarpal ;   while   the 
remaining-  articulations  vary  in  form  with  the  varying-  surfaces 
found   upon  the  extremities  of  the   metacarpal   bones  and  the 
corresponding-  surfaces  on  the  carpal.      TJie  articulations  be- 
izveen  the  carpal  bones  themselves  have  been  mentioned  in  the 
description  of  those   bones.     It  will   be  noticed  that  none  of 
these   bones  are  articular    on    their    posterior    and    anterior 
aspects,  thoug-h  it  is  said  that  the  cuneiform  is  articular  ante- 
riorly and  the  pisiform  posteriorly,  but  these  surfaces  do  not 
look  directly   forward  and    backward.     When    viewed   from 
its  posterior  aspect,  the  first  row   presents  a  set  of  but  three 
bones,  the   pisiform   not  being-  seen   from   the  posterior  face. 
It  will  be  noticed  that  the  carpal  bones  taken  as  a  whole  form 
an  arch  whose  concavity  is  directed  to  the  front,  and  whose 
convexitv  is  directed  backward.     Hence  it  can  be  readily  seen 
that   all  of  the   bones  of  the  carpus,  with  the  two  exceptions 
mentioned,  are   broader   upon  their  posterior  than  upon  their 
anterior  aspect.     This  arch   of  course  g-ives  streng-th   to  the 
hand,  while  at  the  same  time  permitting  the  necessary  flexibility. 


32  DESCRIPTIVE  ANATOMY. 

Metacarpus. 

The  metacarpus  is  formed  by  five  bones  classed  as  long- 
bones  ;  four  of  these,  for  the  four  fiug-ers,  being-  nearly  paral- 
lel, while  the  fifth — for  the  thumb — recedes  from  the  others 
as  it  descends.  The  metacarpal  bones  articulate  above  with 
the  lower  row  of  the  carpus  ;  below  with  the  upper  extremity 
of  the  first  phalanges.  At  their  upper  ends  they  articulate 
laterally  with  one  another,  except  the  metacarpal  bone  of  the 
thumb  ;  but  at  the  lower  end  they  do  not  articulate  with  one 
another.  The  metacarpus,  like  the  carpus,  is  arched  trans- 
versely, the  convexity  being  posterior.  One  of  its  constitu- 
ents may  be  thus  described  : 

A  Typical  Metacarpal  Bone. 

The  Metacarpal  Bones  are  long-  bones,  presenting-  a  shaft 
and  two  extremities,  the  upper  extremity  called  the  base  and 
the  lower  called  the  head.  The  upper  extremity  is  quadri- 
lateral ;  and  it  presents  anterior  and  posterior  surfaces,  of 
which  the  posterior  surface  is  the  broader,  these  two  surfaces 
being-  roughened  for  ligamentous  attachment;  two  lateral 
surfaces,  which  are  marked  by  articular  facets,  intended  for 
articulation  with  the  adjoining  metacarpal  bones. 

The  Summit  of  the  bone  is  marked  by  a  quadrilateral 
articular  facet,  for  articulation  with  one  of  the  carpal  bones 
of  the  second  row. 

The  Lozver  Extremity,  or  head,  terminates  in  an  articular 
surface,  oblong  antero-posteriorly,  and  articular  higher  up  in 
front  than  behind.  On  either  side  of  this  surface  is  a  depres- 
sion, and  behind  this  depression  is  a  well-marked  tubercle. 
Posteriorly  the  lower  extremity  is  flattened  and  rough,  while 
anteriorly  it  presents  a  slight  groove,  caused  by  the  passag-e 
of  the  tendons  of  the  flexor  muscles. 

The  Shaft  is  triangular  and  arched,  with  the  convexity 
of  the  arch  directed  backward.  It  presents  a  posterior  and 
two  lateral  faces,  an  anterior  and  two  lateral  borders.  The 
posterior  face    at    its    upper    end    presents   a   median    Ion- 


OSTEOLOGY.  33 

g-itudimal  ridgfe,  with  a  slig-ht  depression  upon  either  side 
of  it.  This  ridg-e,  as  it  passes  downward,  divides  about 
the  middle  of  the  bone  into  two,  each,  graduall}'-  sepa- 
ratinor,  descends  to  reach  the  tubercle  above  the  lateral  de- 
pression on  the  lower  extremity.  The  triang-ular  space 
between  these  diverg-ing-  ridg-es  is  flattened.  The  lateral 
faces  are  concave  and  smooth  from  above  downward,  so  that 
each  pair  of  bones  would  leave  between  them  a  space  for  the 
attachment  of  muscles.  These  are  known  as  the  interosseous 
spaces.  The  bone  is  concave  towards  its  anterior  aspect,  and 
marked  by  the  anterior  border,  which  is  a  rather  indistinct 
vertical  ridg^e  separating"  the  lateral  faces  from  one  another. 

This  description  applies  more  or  less  closely  to  all  the 
metacarpal  bones;  but  each  possesses  appearances  character- 
istic of  itsell,  by  which  it  may  be  discriminated.  E^ach  bone 
is  known  by  the  name  of  the  fing"er  which  it  supports;  but  the 
metacarpal  bones  are  also  known  by  numbers  from  without 
inward. 

The  Metacarpal  Bone  of  the  Thumb  is  the  shortest  and 
larg"est.  Its  posterior  surface  is  broader  and  flatter  than  the 
remaining-  bones,  and  its  lateral  borders  are  more  distinctly 
marked  w^hile  upon  its  summit  it  bears  a  saddle-shaped  or 
concavo-convex  articular  surface,  concave  from  before  back- 
ward, and  convex  from  side  to  side.  This  with  the  absence 
of  any  lateral  articular  facet  will  disting-uish  it  from  the  other 
bones  of  the  metacarpus. 

The  Metacarpal  Bone  of  the  Index  Fing-er  is  the  long-est, 
is  next  in  size  to  that  of  the  thumb,  while  its  base  presents 
three  articular  facets,  two  of  which  are  upon  the  summit,  one 
flattened  for  articulation  with  the  trapezium,  one  concave  for 
articulation  with  the  trapezoid,  and  one  upon  the  internal 
lateral  aspect  for  articulation  wnth  the  metacarpal  bone  of  the 
second  fing^er. 

The  Metacarpal  Bone  of  the  Second  Finger  is  next  in  size 
and  in  length.  On  its  base  it  presents  an  articular  facet  for 
the  OS  magnum;  on  its  outer  lateral  aspect  an  articular  facet 
for  the  metacarpal  bone  of  the  index  finger;  on  its  inner  lateral 

Des  Anat — 3 


34  DESCRIPTIVE  ANATOMY. 

aspect  an  articular  facet  for  the  metacarpal  bone  of  the  ring- 
fing-er,  while  its  upper  outer  posterior  aspect  is  prolong-ed 
into  a  styloid  process,  projecting-  upward  between  the  trape- 
zoid and  the  os  mag-num.  On  its  inner  lateral  aspect  the 
articular  facet  is  divided  into  two  by  a  g-roove. 

The  Metacarpal  Bone  of  the  Ring-  Finger,  next  in  size  and 
length,  is  the  typical  metacarpal  bone.  On  its  external  lateral 
aspect  a  groove  divides  the  articular  facet  into  two  for  the 
two  corresponding-  facets  on  the  inner  lateral  aspect  of  the 
metacarpal  bone  of  the  middle  fing-er. 

The  Metacarpal  Bone  of  the  Little  Fing-er  is  the  smallest. 
Its  base  presents  a  superior  articular  facet  for  the  unciform, 
and  a  lateral  facet  on  its  outer  aspect  for  the  corresponding- 
facet  on  the  metacarpal  bone  of  the  middle  fing-er.  On  the 
inside  of  the  base  is  a  rough  and  prominent  tuberosity  with  no 
lateral  articular  facet,  which  in  itself  disting-uishes  it  from  the 
other  metacarpal  bones. 

The  Phalanges. 

The  Phalang-es  consist  of  three  rows  of  long-  bones,  extend- 
ing from  the  heads  of  the  metacarpal  bones  to  the  tips  of  the 
fingers.  The  rows  are  numbered  from  the  metacarpal  bones, 
first,  second,  and  third,  the  third  row  being-  usually  called 
ungual. 

The  Thumb  has  but  two  phalang-es,  the  second  phalanx 
taking-  the  place  of  the  characteristic  ung-ual  or  third. 

The  first  phalanx  is  the  long-er,  and  its  shaft  is  semi-cylin- 
drical. The  posterior  surface  is  convex  both  from  above  down- 
ward and  from  side  to  side  and  is  smooth.  The  ante- 
rior surface  is  slightly  curved  longitudinally,  and  is  broader 
above  than  below.  The  two  lateral  borders,  well-marked 
above,  terminate  in  slight  tubercles  at  the  lower  aspect  of  the 
bone.  The  Base  or  Upper  Extremity  presents  a  smooth 
round  shallow  articular  facet,  whose  transverse  diameter  is 
slig-htly  g-reater  than  the  antero-posterior,  and  it  is  almost  cup- 
shaped.  This  is  for  articulation  with  the  head  of  the  meta- 
carpal bone.  The  Head  or  Lozuer  Extremity  presents  an 
antero-posterior  g-roove,  surmounted  on  either  side  by  an  artic- 


OSTEOLOGY.  35 

ular  ridg-e,  constituting-  a  trochlear  surface.  On  either  side  of 
the  head  is  a  slig-ht  depression,  marked  in  front  and  behind  by- 
trifling'  elevations  or  tubercles. 

The  second  phalanx  presents  on  its  base  a  receiving-  surface 
for  the  trochlea  ;  that  is,  a  central  ridg-e  with  lateral  depres- 
sions to  receive  the  corresponding-  elevations.  Like  the  first 
phalanx  it  is  broad  and  expanded  above,  narrower  below. 
Its  lower  extremity  presents  a  trochlea  for  articulation  with 
the  third,  or  ung-ual  phalanx.  The  second  phalanx  with  the 
exception  of  the  head  is  like  the  first,  only  it  is  shorter  and 
less  massive. 

The  Third,  or  Ung-ual  Phalanx  (Z.  Ung-nis,  a  nail)  presents 
on  its  base  an  articular  surface  to  receive  the  trochlea  of  the 
second.  It  then  becomes  rapidly  narrow  ;  but  just  before  it 
terminates,  it  expands  into  a  broadened  surface.  The  bone  is 
smooth  on  its  posterior,  but  roug-h,  prominent  and  flat  on 
its  anterior  surface.  The  posterior  aspect  of  this  phalanx 
supports  the  nail,  while  the  anterior  surface  supports  the  tis- 
sues which  form  the  pulp  of  the  corresponding-  fing-ers. 
There  being-  but  two  phalang-eal  bones  for  the  thumb,  the 
second  phalanx  for  the  thumb  corresponds  to  the  ung-ual 
phalanx  for  the  other  fing-ers. 

The  Skeleton  of  the  Lower  Extremity. 

The  skeleton  of  the  lower  extremity  consists  of  the  skeleton 
of  the  hip,  thig-h,  leg-  and  foot. 

Os  Innominatum. 

The  Os  Innominatum  (L.  Theun-named  bone)  haunch  bone, 
is  the  most  important  bone  in  forming-  the  pelvic  cavity,  and 
corresponds  to  the  Scapula  in  the  upper  extremity.  In  the 
foetus  it  consists  of  three  bones — Ilium,  Ischium  and  Pubis, 
and,  since  the  bone  is  very  irreg-ular  in  outline,  this  division 
has  been  retained  in  describing-  the  bone  in  the  adult. 

The  Ilium  (Deriv.  uncertain)  or  flank  bone,  is  the  larg-e, 
expanded,  upper  j)ortion  of  the  bone.  It  is  divided  for  study 
into  and  internal  and  external  surface,  anterior,  posterior, 
and  superior  borders,  the  latter  being-  known  as  the  crest. 


36  DESCRIPTIVE  ANATOMY. 

The  crest  of  the  ilium  is  sinuous  in  outline.  Viewed  from 
in  front  it  is  seen  to  be  convex  for  its  anterior  four  fifths,  con- 
cave for  its  posterior  one  fifth.  In  front  and  behind  it  termin- 
ates in  roug^h  projections,  known  as  the  anterior  and  posterior 
superior  spinous  processes.  The  crest  consists  of  two  lips, 
external  and  internal,  and  a  roug-h  intervening-  space  or  middle 
lip.  The  anterior  border  consists  of  two  projections,  anterior 
superior  and  anterior  inferior  spinous  processes,  with  a  notch 
between.  The  superior  is  more  prominent  but  less  massive  than 
the  inferior.  Below  the  inferior  is  a  slig^ht  g^roove  separating*  it 
from  the  margin  of  the  acetabulum.  The  posterior  border  is 
less  reg-ular  in  form  than  the  anterior  and  like  it,  is  marked  by 
two  projections  with  an  intervening-  notch.  These  are  called 
the  posterior  superior  and  posterior  inferior  spinous  processes. 
They  are  sharper  and  less  distinctly  marked  than  those  on  the 
anterior  border,  and  the  notch  between  is  not  so  deep.  Below 
the  posterior  inferior  spinous  process  is  a  deep  notch,  part  of 
which  is  found  on  the  ilium  and  the  remainder  on  the  ischium, 
called  the  g"reater  sacro-sciatic. 

The  external  surface  is  curved  in  outline  being-  concave  for 
the  posterior  four  fifths,  convex  for  the  anterior  one  fifth.  On 
the  posterior  border  is  a  deep  notch,  called  g-reat  sciatic,  and 
commencing-  in  this  notch,  and  curving-  forward  and  upward 
from  it,  are  three  lines  disting-uished  as  superior,  inferior  and 
middle.  The  superior  curved  line,  the  shortest  and  most 
distinct  of  the  three,  beg-ins  near  the  upper  marg-in  of  the 
sciatic  notch  and  passes  upward  and  slig-htly  forward  until  it 
reaches  the  crest  near  its  posterior  one  filth.  The  middle,  which 
is  the  long-est,  beg-ins  at  the  middle  of  the  sciatic  notch  and 
passes  upward  and  forward,  markedly  curved,  to  terminate 
just  above  the  anterior  superior  spinous  process.  The  inferior, 
the  least  distinct,  starts  at  the  lower  portion  of  the  notch  and, 
passing-  forward  and  slig-htly  upward,  reaches  the  anterior 
border  of  the  bone  a  little  above  the  anterior  inferior  spinous 
process.  The  whole  surface  is  roug-hened  for  the  attachment 
of  muscles  and  presents  the  orifices  of  numerous  foramina  for 
the  transmission  of  blood  vessels,  the  larg-estof  which  is  found 
near  the  middle  of  the  bone  just  below  the  middle  curved  line. 


OSTEOIvOGY.  37 

The  internal  surface,  much  smoother  than  the  external,  is 
concave  for  its  anterior  two  thirds  both  from  above  downward 
and  from  before  backward,  forming*  the  iliac  fossa.  Just  be- 
fore the  bone  unites  with  the  ischium  it  is  crossed  by  a  smooth, 
elevated  ridge  which  forms  a  part  of  the  ilio-pectineal  line. 
The  portion  of  bone  below  this  is  smooth,  nearly  flat,  continu- 
ous with  the  inclined  plane  of  the  ischium,  and  enters  into  the 
formation  of  the  true  pelvis.  The  posterior  one  third  of  the 
internal  surface  is  very  irregular  in  outline.  In  front  this  sur- 
face is  occupied  by  a  roug-h,  ear  shaped  articular  surface  which 
articulates  with  a  similar  surface  on  the  sacrum.  Behind  this 
is  a  roug-h  surface,  made  up  of  intervening-  elevations  and 
depressions  for  the  attachment  of  lig-amentous  fibres. 

The  Ischium  is  the  lower,  massive  portion  of  the  bone.  It 
is  divided  for  study  into  a  body,  tuberosity  and  ramus.  The 
body  is  triang-ular  and  presents  for  examination  three  surfaces 
and  three  borders.  The  surfaces  are  internal,  external  and 
posterior;  the  borders,  anterior,  posterior  and  external.  Nearly 
the  whole  of  the  external  surface  is  occupied  by  the  articular 
surface  furnished  by  the  ischium  to  the  acetabulum;  but  a  small 
portion  below  the  rim  of  the  acetabulum  is  occupied  by  a 
g-roove,  the  lower  border  of  which  is  the  mark  of  division 
between  the  outer  surface  and  the  tuberosity.  The  internal 
surface  slopes  obliquely  from  above  downward  and  inward, 
facing-  inward  and  backward.  It  is  smooth  and  concave  from 
before  backward  and  continuous  above  with  a  similar  surface 
on  the  inner  face  of  the  ilium.  The  posterior  surface  is 
quadrilateral,  forms  the  posterior  wall  of  the  acetabulum  and 
is  roug-hened  for  muscular  attachment.  The  anterior  border 
is  thin  and  sharp,  slopes  upward  and  forward  to  join  the  pubes 
and  forms  the  posterior  boundary  of  the  thyroid  foramen. 
The  external  border  is  thick  and  rounded  and  forms  the 
posterior  part  of  the  rim  of  the  acetabulum.  The  posterior 
border  is  long-  and  sharp,  nearl}'  vertical  in  direction  and  is 
interrupted  a  little  below  the  middle  by  a  prominent  projection 
of  bone  called  the  spine  of  the  ischium.  Above  the  spine  a 
deep  notch  is  found  which   enters   into  the   formation  of  the 


38  DESCRIPTIVE  ANATOMY. 

great    sacro-sciatic    notch;    below    the   spine,   a    similar,    but 
shallower  notch  forms  the  lesser  sacro-sciatic  notch. 

The  tuberosity  is  the  rough  lower  end  of  the  bone  on  ^vhicli 
the  body  rests  w-'hen  in  the  sitting-  posture.  It  has  an  inferior 
surface  w^hich  is  roug-h  and  triang-ular,  and  just  above  this,  a 
smooth  portion,  divided  into  two  bv  an  oblique  ridge,  the  parts 
above  and  below  the  ridge  being  intended  for  muscular 
attachment.  Internally  it  presents  a  rough,  prominent  ridge 
which  separates  the  lower  surface  from  the  internal,  and 
above  this  ridge  a  smooth  g-roove. 

The  Ramus  passes  forward,  inw^ard  and  slightly  up- 
ward. One  surface  looks  outward  and  forward,  the  other 
inward  and  backward.  One  border  looks  outw^ard  and 
forms  the  anterior  boundary  of  the  obturator  foramen, 
the  other  looks  inward  and  forms,  with  the  ramus  of 
the  pubis,  the  outer  boundary-  of  the  pubic  arch.  This 
internal  border  is  thick  and  divided  into  two  lips  and  an  inter- 
vening space.  The  two  lips  pass  downw^ard  to  become  con- 
tinuous with  similar  lips  on  the  lower  surface  of  the  tuberos- 
ity. The  internal  border  is  averted,  its  upper  part  looking 
nearl}"  forward.  At  the  junction  of  the  ramus  of  the  ischium 
with  that  of  the  pubes  there  is  sometimes  seen  a  rough  line. 

The  Os  Pubis  iL.  Pubes,  hair,  or  down)  is  divided  for 
stud}^  into  a  body  and  a  ramus.  The  body  is  the  horizontal 
portion  of  the  bone,  and  is  divided  into  two  surfaces,  anterior 
and  posterior,  two  borders,  upper  and  lower,  and  tw^o  extremi- 
ties, internal  and  external. 

The  posterior  surface  is  concave  from  before  backward, 
convex  from  above  downward  and  smooth.  The  anterior 
surface  is  convex  from  before  backward,  slightly  concave 
from  above  downward,  broad  at  its  inner  and  narrow  at  its 
outer  extremity,  and  rough  for  muscular  attachments.  The 
superior  border  is  marked  at  its  junction  with  the  internal 
extremity  by  the  angle  of  the  pubis;  external  to  this  and  run- 
ning outward  and  forward  is  a  rough  ridge  called  the  crest. 
The  crest  terminates  after  a  course  of  about  three  fourths  of 
an  inch  in  a  prominent  projection  of  bone  called   the  spine. 


OSTEOLOGY.  39 

Runningf  outward  and  backward  from  the  spine  and  separating- 
the  superior  border  from  the  posterior  surface,  is  a  sharp 
ridg-e  of  bone  called  the  pectineal  line;  in  front  of  which  is  a 
triang"ular  surface,  limited  in  front  by  the  anterior  surface  of 
the  pubis,  the  pectineal  triang-le.  The  base  of  the  triangle, 
which  is  directed  outward,  terminates  in  a  rough  prominence 
known  as  the  pectineal  eminence.  The  inferior  border  forms 
the  superior  boundary  of  the  thyroid  foramen  and  is  marked 
by  an  oblique  g-roove,  which,  from  within  the  pelvis,  extends 
forward  and  inward.  The  internal  extremity,  called  the 
symphysis  pubis,  is  an  oval,  roug^h  articular  surface,  the  long- 
diameter  of  which  is  directed  from  above  downward  and  back- 
ward. It  is  covered  by  a  series  of  nipple  shaped  projections 
and  in  the  recent  state  is  lined  with  cartilag-e.  The  external 
extremity  is  in  part  attached  to  the  ilium,  while  the  remainder 
is  free  and  enters  into  the  formation  of  the  acetabulum. 

The  ramus  of  the  pubes  is  short  and  extends  downward 
and  slightly  outward.  Its  surfaces  look  backward  and  for- 
ward, its  borders  inward  and  outward.  The  inner  border 
presents  two  lips  and  an  intervening-  space,  the  two  lips  being 
continuous  with  those  found  on  the  ramus  of  the  ischium. 

The  acetabulum  (L.  a  vessel  for  holding-  vinegar,  from  a 
supposed  resemblance)  is  a  nearly  circular,  cup-shaped  cavity, 
one-fifth  of  which  is  contributed  by  the  pubes,  a  little  less 
than  two-fifths  by  the  ilium  and  a  little  more  than  two-iifths 
by  the  ischium.  It  is  articular  around  the  whole  of  its  cir- 
cumference except  a  small  portion  at  the  lower  and  inner  part, 
where  a  deep  notch  interrupts  the  prominent  rim  which  else- 
where surrounds  the  cavity.  This  notch,  called  the  cotyloid, 
leads  to  a  deep  non-articular  depression  in  the  bottom  of  the 
cavity,  which  in  the  recent  state  lodg-es  amass  of  fat  and,  with 
its  margins,  g-ives  attachment  to  the  ligamentum  teres. 

The  thyroid  or  obturator  foramen  is  found  below  and  in 
front  of  the  acetabulum.  It  is  irregularly  oval  in  outline  and 
its  boundaries  are  formed  as  follows  :  Behind  by  the  anterior 
border  of  the  body  of  the  ischium,  in  front  bv  the  outer  border 
of  the  ischilo-pubic  rami,  above  by  the  lower  border  of  the  body 


40  DliSCRIPTlVE  ANATOMY. 

of  the  pubes,  the  groove  on  that  bone  furnishing-  nearly  the 
whole  of  the  upper  boundary. 

Pelvis. 

The  Pelvis  (L.  a  basin  or  laver,  from  a  resemblance  to  an 
ancient  basin.)  The  pelvic  g"irdle  is  far  more  powerful  than 
the  shoulder  g-irdle,  the  individual  bones  being  more  massive 
and  bound  more  firmly  to  one  another.  The  cavity  has  been 
divided  by  the  ilio-pectineal  line,  into  the  true  and  the  false 
pelvis,  thoug-h  the  latter  term  should  not  be  used,  since  the 
false  pelvis  is  simply  a  part  of  the  abdominal  cavity. 

The  pelvis  is  the  cavity  circumscribed  by  the  sacrum,  coc- 
cyx and  two  ossa  innominata,  containing-  in  the  living-  subject 
some  of  the  small  intestine,  a  part  of  the  larg-e  intestine,  and 
the  genito  urinary  apparatus,  in  part.  It  is  bounded  behind 
by  the  sacrum  and  coccyx  and  throug-hout  the  rest  of  its  ex- 
tent by  the  ossa  innominata.  It  is  divided  into  two  portions, 
the  false  pelvis  and  the  true.  The  false  pelvis  is  that  por- 
tion between  the  two  iliac  fossae  bounded  behind  by  the 
junction  of  5th  lumbar  and  sacrum,  while  in  front  it 
has  no  bony  wall.  It  extends  from  the  crest  of  the  ilium 
above  to  the  pectineal  line  below.  This  pectineal  line, 
also  called  linea  ilio-pectinea,  is  a  prominent  ridg-e  extend- 
ing around  the  os  innominatum  from  the  symphysis  pubis 
to  the  sacro-iliac  symphysis.  At  the  linea  ilio-pectinea  the 
pelvis  is  suddenly  contracted  and  the  true  pelvis  beg-ins. 
The  plane  circumscribed  by  the  ilio-pectineal  line  is  called, 
the  brim  or  inlet  of  the  pelvis,  or  superior  strait  of  the  pelvis. 
The  true  pelvis  thus  extends  from  this  brim  downward  to 
what  is  called  the  outlet,  or  inferior  strait  of  the  pelvis.  The 
outlet  is  limited  in  front  by  the  lower  end  of  the  symphysis 
pubis;  the  arch  formed  by  the  diverg-ence  of  the  pubic  rami 
being  called  the  pubic,  or  sub-pupic  arch.  Behind,  the  outlet 
is  limited  by  the  tip  of  the  coccyx.  Laterally  the  outlet  is 
bounded  by  the  tuber  ischii.  The  pelvis  is  so  attached  to  the 
vertebral  column  as  to  render  the  plane  of  the  inlet  oblique, 
from  behind  downward  and  forward,  and  so  g-reat  is  this  obli- 
quity that  the  top  of  the  symphysis  pubis  is  about  four  inches 


OSTEOLOGY.  41 

below  the  level  of  the  promontory  of  the  sacrum.  The  so- 
called  axis  of  the  superior  strait  is  an  imag-inary  line,  perpen- 
dicular to  the  plane  of  the  brim  and  cutting-  it  at  its  centre. 
The  true  pelvis  is  much  deeper  behind  than  in  front,  measuring" 
posteriorly  five  inches,  latterally  three  and  one-half  inches, 
and  at  the  pubes  one  and  one-half  inches.  Besides  these  meas- 
urements, obstetricians  employ  others,  as  of  the  outlet  and 
inlet,  called  diameters.  The  diameters  usually  g-iven  are  for 
the  inlet,  antero-posterior  and  transverse. 

The  objects  observable  on  the  exterior  of  the  pelvis  are  as 
follows:  in  front  the  symphysis  pubis  and  below  this  the 
pubic  arch;  on  either  side  the  obturator  foramen,  farther  out 
the  acetabulum;  behind  this  the  g-reater  and  lesser  sciatic 
notches,  separated  by  the  ischiatic  spine;  on  the  centre  behind 
are  the  sacral  spines. 

The  pelvis  differs  in  the  two  sexes;  the  characteristic  points 
in  the  female  are  as  follows:  1st,  the  thyroid  foramen  is  more 
distinctly  triang-ular;  2d,  the  pelvis  is  more  capacious — meas- 
uring" more  transversely  and  antero-posteriorly,  but  less  ver- 
tically; 3d,  the  ang-le  of  the  pubic  arch  is  g-reater  by  10°, 
measuring-  from90°  to  100°. 

The  pelvis  in  the  neg-ro  is  observably  smaller  than  in  the 
Caucasian. 

The  Femur. 

The  Femur  (Z.  Femur,  the  thig-h)  is  the  long-est  and  most 
powerful  bone  in  the  body.  It  is  divided  for  study  into  a 
shaft  and  two  extremities.  The  upper  extremity  presents  a 
head,  neck  and  two  tuberosities  called  trochanters. 

The  Upper  Extremily  consists  of  the  head,  neck  and  two 
trochanters. 

The  Head,  smooth  and  g-lobular,  projects  upward,  inward 
and  forward  from  the  neck,  and  forms  about  two  thirds  of  a 
sphere.  It  is  marked  a  little  below  and  behind  its  centre  by 
a  deep  pit  which  in  the  recent  state  lodg-es  the  outer  end  of 
the  lig-imentum  teres.  The  neck  slopes  downward,  outward 
and  backward  from  the  head,  is  flattened  from  before  back- 
ward and  is  divided  into  an  anterior,  and  posterior  surf  ice,  an 


42  DESCRIPTIVE  ANATONY. 

Upper  and  a  lower  border.  The  anterior  surface  is  flat  and 
slightly  roughened  ;  the  ^posterior,  convex  from  above  down- 
ward, concave  from  within  outward,  is  smooth  and  rounded. 
The  upper  border,  only  one  half  the  length  of  the  lower,  is 
broad,  round,  thicker  than  the  lower  and  marked  at  its  outer 
extremity  by  a  deep  pit  called  the  digital.  It  is  nearly 
straight.  The  lower  border  is  thinner,  longer  and  more 
oblique  than  the  upper.  B2I0W  and  behind  it  terminates  at 
the  lesser  trochanter  while  the  upper  terminates  at  the  greater 
trochanter.  The  great  trochanter  is  a  quadrilateral  piece  of 
bone  which  projects  upward  from  the  junction  of  the  neck  and 
shaft.  Its  outer  surface  is  marked  by  an  oblique  ridge;  a  di- 
agonal, running  from  the  postero-superior  angle  to  the  antero- 
inferior angle.  The  surface  in  front  of  the  diagonal  is  rough, 
that  behind  it  is  smooth.  The  inner  surface  is  taken  up  almost 
entirely  by  the  digital  pit.  The  anterior  border  is  thick  and 
rough,  the  posterior,  thinner  and  rounded,  the  upper  thin 
and  rather  sharp,  terminating  posteriorly  in  a  blunt  pro- 
jection which  overhangs  the  digital  pit.  The  lesser  trochan- 
ter is  much  smaller  than  the  greater,  projects  from  the  inner 
posterior  aspect  of  the  bone,  is  round  in  form,  bluntly  pointed 
at  its  apax  and  marked  by  a  single  muscular  impression  for 
the  attachment  of  the  biceps  flexor  femoris.  Extending  from  the 
base  of  the  great  trochanter  downward  and  inward  to  the  lesser  is 
a  roughened  ridge  of  bone  known  as  the  posterior  inter-trochan- 
teric  line.  On  the  anterior  aspect,  and  starting  from  the  base 
of  the  great  trochanter,  there  is  a  more  prominent  line  which 
winds  around  the  bone,  pissing  downward  and  inward  until 
it  reaches  the  inner  face  of  the  bone  when  it  turns  and  runs 
outward,  called  the  spiral  line  of  the  femur.  This  line  is 
sometimes  incorrectly  called  the  anterior  inter-trochanteric 
line.  It  passes  about  half  an  inch  below  the  lesser  trochanter. 
The  Lozuer  Extremity  of  the  femur  is  flattened  from  before 
backward,  so  that  the  lateral  diameter  exceeds  the  antero- 
posterior. It  consists  of  two  round  or  oval  articular  surfaces, 
called  condyles,  two  rough  projections,  one  on  either  side, 
called  tuberosities,  and  an  intervening  notch.     If  the  bone  is 


OSTEOLOGY.  43 

held  vertically  it  will  be  seen  that  the  inner  condyle  is  pro- 
lonored  downward  considerably  below  the  outer  to  compensate 
for  the  obliquity  of  the  bone  caused  by  the  width  of  the  pelvis, 
which  separates  the  heads  of  v  the  bone,  while  the  lower 
extremities  approach  each  other.  The  long-  diameter  of  the 
articular  surface  of  each  condyle  is  from  before  backward  ; 
but  it  will  be  seen  upon  careful  examination  that  the  inner 
condyle  is  long-er  and  narrower  than  the  outer,  that  its 
articular  surface  extends  hig-her  up  behind  and  not  so  hig-h 
in  front.  The  outer  condyle  is  more  oval,  is  shorter  than 
the  inner,  its  articular  surface  extending-  hig-her  up  in  front 
than  behind.  The  two  condvles  are  separated  behind  by  a 
deep  and  roug-hened  notch,  called  the  intercondyloid  notch. 
This  notch  is  marked  on  either  side  by  a  depression  for  the 
attachment  of  the  corresponding  crucial  lig^aments  of  the  knee- 
joint.  In  front  this  notch  is  continuous  with  a  smooth  articu- 
lar surface,  concave  from  side  to  side,  convex  from  above 
downward,  and  forms  a  trochlea  for  the  opposite  surface  of  the 
patella.  Each  condyle  presents  an  internal  and  an  external 
surface.  The  external  surface  of  the  external  condyle  is 
marked  by  a  prominent  roug-h  tuberosity,  called  the  outer 
tuberosity  of  the  femur;  and  below  this  is  an  antero-posterior 
g"roove  for  muscular  attachments.  The  internal  surface  of 
the  external  condyle  is  the  outer  boundary  of  the  intercondy- 
loid notch.  The  internal  surface  Q>i  the  internal  condyle  is 
likewise  marked  by  a  roug-h  projection,  called  the  internal 
tuberosity  oj  the  femur;  while  the  outer  surface  of  the  inter- 
nal condyle  is  the  inner  boundary  of  the  intercondyloid  notch. 
The  inner  surface  of  the  inner  and  the  outer  surface  of  the 
outer  condyles  are  each  marked  by  nutrient  foramina.  Above 
each  condyle  is  seen  a  slig^ht  depression  on  the  posterior  aspect 
of  the  bone,  which  is  intended  for  the  attachment  of  the  g"as- 
trocnemius  muscle.  Leading-  upward  from  either  condyle  is  a 
ridge.  These  ridg-es  approach  each  other  above  to  reach  the 
linea  aspera.  They  are  known  as  the  condyloid  ridges,  and 
more  properly  belong-  to  the  shaft  of  the  bone.  Between  these 
ridg-es  is  a  triangular  roughened  space  called  the  Popliteal 
Triangle. 


44  DESCRIPTIVE  ANATOMY. 

The  Shaft  of  the  Femur.  Like  most  long-  bones  the  femur 
is  triangular  upon  cross-section  ;  and  therefore  presents  for 
study  three  surfaces  and  three  borders.  The  surfaces  are 
anterior  and  two  lateral ;  while  the  borders  are  posterior  and 
two  lateral. 

The  anterior  surface  is  round,  convex  from  above  down- 
w^ard,  so  that  the  bone  is  bowed  in  outline,  with  its  convexity 
forward,  convex  from  side  to  side,  and  broader  above  and 
below  than  in  the  middle.  Of  the  two  lateral  surfaces,  the 
external  is  slig-htly  concave  fromabove  downward,  and  smooth; 
the  inter)ial  also  slightly  concave  from  above  downward, 
broader  than  the  external,  and  smooth.  The  lateral  borders 
are  indistinctly  marked.  The  external  lateral,  commencing-  at 
the  base  of  the  trochanter  major,  extends,  indistinctlv  marked, 
down  to  the  outer  tuberosity  of  the  femur.  The  internal  lateral^ 
commencing-  at  the  spiral  line  of  the  femur,  passes  downward  to 
the  inner  tuberosity.  The  -posterior  border,  called  linea  as-pera 
is  the  most  distinct  of  the  three.  It  may  be  considered  as  con- 
sisting- of  a  central  portion,  called  the  "body  ;"  and  an  upper 
and  a  lower  portion.  The  central  portion,  or  body,  occupies 
about  the  middle  two-fourths  of  the  bone.  It  presents  an 
internal  and  an  external  lip,  and  a  roug-h  intervening-  space, 
which  are  intended  for  muscular  attachments.  Above  it 
divides  into  three  lines  :  one  winds  around  about  a  quarter  of 
an  inch  below  the  lesser  trochanter  to  become  continuous  wnth 
the  spiral  line  of  the  femur ;  one  passes  upward  to  the  base  of 
the  lesser  trochanter  ;  while  the  vertical  passes  upward  and 
outward  to  join  the  posterior  border  of  the  g-reater  trochanter. 
Below  it  subdivides  into  two  ridges,  which  are  known  as  the 
two  condyloid  ridges.  These  two  ridges  diverge  from  each 
other,  enclosing  the  -popliteal  space,  a  smooth  triangular 
space  found  at  the  lower  extremity  of  the  shaft,  the  base  of 
which  is  directed  downward  to  the  condyles  and  the  apex  up- 
w^ard  to  the  linea  aspera.  Of  these  two  lines  the  external 
is  the  more  distinct,  the  internal  being  obliterated  near  its 
middle  by  the  groove  which  transmits  the  femoral  artery. 
About  the  middle  of  the  shaft  of  the  bone,  and  rising  either  in 


OSTEOLOGY.  45 

the  linea  aspera  or  upon  its  external  surface  close  to  the  linea 
aspera,  is  found  a  larg-e  nutrient  foramen,  which  is  directed 
obliquely  upward  and  outward. 

The  Patella. 

The  Patella  (Iv.  Patella,  a  small  pan),  or  knee-pan,  is  a 
sesamoid  bone  situated  on  the  front  of  the  knee  joint,  devel- 
oped in  the  tendon  of  the  triceps  extensor  cruris.  It  presents 
for  examination  two  surfaces,  anterior  and  posterior,  two 
extremities,  superior  and  inferior,  and  two  borders,  internal 
and  external.  The  aiiterior  surface  is  rough,  marked  by  a 
number  of  vertical  lines  and  a  number  of  nutrient  fora- 
mina. The  posterior  surface  is  smooth  and  articular. 
Near  its  middle  it  presents  a  prominent  vertical  ridg-e  ; 
and  on  either  side  of  this  a  depression,  also  articular,  in- 
tended for  the  reception  of  the  condyles  of  the  femur.  The 
posterior  face  forms  the  receiving-  surface  for  the  trochlea. 
These  depressions  are  dissimilar  in  size  and  shape  ;  and  cor- 
respond to  the  dissimilarity  of  the  condyles  of  the  femur,  the 
outer  depression  being  larger  and  more  nearly  circular,  while 
the  inner  is  smaller  and  more  oval  in  outline.  The  upper 
extremity  of  the  bone  is  blunt,  rough,  and  marked  by  a  trans- 
verse ridge  ;  the  lower  extremity,  smaller  and  more  pointed, 
is  roughened.  Of  the  borders,  the  external  is  thinner  and 
sharper  than  the  iutcrnal.  Both  are  roughened  for  the  attach- 
ment of  the  tendinous  fibres  of  the  triceps. 

The  Tibia. 

The  Tibia  (Z.  Tibia,  a  flute  or  pipe)  is  a  long  bone,  con- 
sisting of  a  shaft  and  two  extremities.  It  is  the  larger  of  the 
two  bones  making  up  the  skeleton  of  the  leg. 

The  Upper  Extremity  is  expanded  so  that  its  transverse 
diameter  is  much  greater  than  its  antero-posterior.  It  pre- 
sents upon  its  summit  two  shallow  articular  cavities,  called 
glenoid  cavities,  intended  to  receive  the  condyles  of  the  femur, 
and  in  correspondence  with  them  are  dissimilar  in  shape,  the 
outer  being  circular  and  the  inner  oval.  The  inner  cavity  has 
its  long  diameter  antero-posterior ;  the  outer  cavity  is  shal- 


46  DESCRIPTIVE  ANATOMY. 

lower,  as  well  as  being-  circular  in  outline.  These  cavities 
are  separated  from  one  another  by  a  prominent  projection, 
which  is  called  the  spine  of  the  tibia.  This  spine  is  bifurca- 
ted ;  and  is  situated  nearer  to  the  posterior  than  to  the  anterior 
surface  of  the  extremity.  In  front  and  behind  the  spine  is 
seen  a  roug-hened,  non-articular  space,  which  is  intended  for 
lig-amentous  attachment.  On  the  front  of  the  bone,  about  an 
inch  below  the  articular  cavities,  is  a  roug^h  triang-ular  space, 
below  which  is  seen  a  projection,  called  the  anterior  tubercle 
of  the  tibia.  This  tubercle  is  smooth  above  and  roug-h  below, 
the  rougfhened  lower  portion  being  intended  for  muscular  at- 
tachment. That  expanded  portion  of  the  bone  upon  which 
the  g-lenoid  cavities  rest  is  known  as  the  tuberosity  of  the  ti- 
bia, internal  and  external.  The  internal  tuberosity,  somewhat 
more  prominent  than  the  external,  is  roug-h,  and  marked  near 
its  posterior  portion  by  a  deep  transverse,  or  antero-posterior 
groove.  The  external  tuberosity  is  roug-hened,  as  is  the  inter- 
nal, and  posteriorly  is  marked  by  a  flat,  circular,  articular 
facet,  which  is  directed  downward,  outward,  and  backward, 
and  is  intended  for  articulation  with  the  upper  extremity  of 
the  fibular.  Behind,  the  tuberosities  are  both  roug-hened  for 
ligamentous  attachment. 

The  Lozver  Extremity  is  four-sided  ;  and  is  about  half 
the  size  of  the  upper.  On  its  inner  side  there  extends 
downward  a  rough  projection  of  bone,  called  the  internal 
malleolus  (L.  A  small  mallet).  It  corresponds  nearly  to 
a  styloid  process.  This  internal  malleoeus  presents  two 
surfaces,  two  borders,  and  an  extremity.  Of  the  sur- 
faces, the  internal  is  rough,  and  subcutaneous,  while  the 
external  is  smooth  triangular  and  articular,  entering  into  the 
formation  of  a  cavity  found  upon  the  extremity  of  the  tibia  for 
articulation  with  one  of  the  bones  of  the  tarsus.  The  anterior 
border  of  the  malleolus  is  shorter  than  the  posterior,  and  is 
vertical  in  its  direction,  while  the  longer  posterior  border  is 
oblique,  extending  downward  and  forward,  and  has  upon  it  a 
well-marked  groove  for  the  transmission  of  a  tendon.  The 
extremity  is  blunt ;  and  is  marked  behind  by  a  pit-like  depres- 


OSTEOLOGY.  47 

siou.  On  the  outer  surface  of  the  lower  extremity  is  a  trans- 
verse depression,  sometimes  articular,  more  g-enerally  roug-h- 
ened,  which  receives  the  lower  extremity  of  the  fibula.  The 
lono-  diameter  of  this  depression  is  directed  from  before  back- 
ward ;  and  leading-  upward  from  it  are  two  lines,  which 
shortly  converg-e,  enclosing*  between  them  a  roug-h  triang-ular 
space  for  the  attachment  of  interosseous  lig-aments.  The 
anterior  aspect  of  the  lower  extremity  is  roug"hened  for  lig'a- 
mentous  attachment,  while  the  posterior,  also  roug-hened,  is 
marked  by  a  vertical  groove.  The  summit  presents  an  artic- 
ular facet,  continuous  with  the  one  on  the  outer  face  of  the 
internal  malleolus,  and  intended  for  articulation  with  the  upper 
surface  of  the  astrag-alus.  This  facet  is  broader  externallj'" 
than  internally,  and  broader  in  front  than  behind.  It  is  con- 
cave from  before  backward,  and  nearly  flat  from  side  to  side. 
The  Shujt  of  the  bone  is  three-sided,  presenting- an  internal, 
an  external,  and  a  posterior  surface,  and  an  anterior  and  two 
lateral  borders.  The  bone  is  g-enerally  somewhat  twisted, 
particularly  in  the  neg-ro  race;  and  is  bowed,  convex  internally 
and  concave  externally.  The  internal  surface  is  broad  above, 
becoming-  slig-htly  narrow  below;  is  convex  both  from  above 
downward,  and  from  before  backward;  and  is  subcutaneous. 
The  external  face,  which  is  concave  from  above  downward,  is 
marked  by  a  vertical  g-roove  close  to  the  external  border  of  the 
bone.  This  face  in  the  lower  third  curves  g-radually  forward 
to  the  anterior  face  of  the  bone.  The  posterior  face  is  broad 
and  flat  for  the  upper  one-fifth  of  the  bone,  becoming-  more 
rounded  in  the  middle  and  flatter  and  broader  in  the  lower 
portion.  At  its  upper  part  it  is  marked  by  an  oblique  ridg-e, 
called  the  Popliteal  Line,  which  extends  downward  and  in- 
ward from  the  external  tuberosity  of  the  bone.  Below  this 
ridg-e  the  posterior  surface  is  marked  about  its  middle  by  a 
■vertical  ridg'e,  which  exists  only  for  about  the  middle  of  the 
bone,  disappearing-  in  the  lower  portion.  Near  the  commence- 
ment of  the  vertical  ridg-e,  g-enerally  on  the  posterior  surface, 
is  found  a  larg-e  nutrient  foramen,  being-  in  fact  the  larg-est  in 
the  body,  which  conveys  the  blood  to  the  interior  of  the  bone. 


4S  DESCRIPTIVE  AXATOLIY. 

Of  the  borders  the  anterior,  or  shin,  is  very  sharp  and  very 
prominent.  It  is  sinuous  in  outline,  more  distinct  in  the  upper 
two-thirds  of  the  bone,  while  in  the  lower  third  it  passes  to 
the  front  of  the  internal  malleolus,  and  blends  with  the  ante- 
rior border  of  this  projection.  The  internal  border,  separating- 
the  internal  from  the  posterior  surface,  begins  as  an  indistinct 
line  at  the  inner  tuberosity,  becomes  more  prominent  about 
the  middle  of  the  bone,  and  finally  passes  to  the  posterior 
border  of  the  internal  malleolus.  The  external  border  com- 
mences above  at  the  outer  malleoeus.  in  :r :  nr  of  the  articular 
facet  for  the  Qbnla.  It  is  the  inter  :s-r  j.s  :  r  i-r,  It  is  indis- 
tinct above,  well  marked  in  the  riiiir  r::  n  of  the  bone, 
and  at  the  low^er  extremity  divides  iiit  t  v  linci,  ^rhich  form 
the  boundaries  of  the  triangular  5p3.cc  rnrnrioned  as  being-  on 
the  loTver  extremity  of  the  bone. 

The  Fibula, 

The  Fibula  (ILr.  Fibiilc.  ?-  cli-.;  is  the  outer  and  more 
sienirr  :  tiie  two  bones  formina;  the  skeleton  of  the  leg.  It 
is  1  i :  ::^   ;: :  ne,  having"  of  course  a  shaft  and  two  extremities. 

The  Upper  Extremity,  or  head,  is  club-like  in  outline,  and 
presents  :n  it-  upper  inner  aspect  an  articular  facet,  the  con- 
: :ur  ::  v  hi  ::  n.ries  in  different  bones.  It  is  circular  in 
form  usually  sliofhtly  concave,  but  it  may  be  flat  and  looks 
upward,  forward  and  inward.  It  is  intended  for  articulation 
\^ith  a  similar  facet  on  the  outer  tuberosity  of  the  tibia. 
The  outer  aspect  of  this  extremity  is  roug^hened  for  muscular 
and  ligamentous  att2.c"nrnent,  and  terminates  above  in  a  blunt 
projection,  called  the  styloid  proce  \     ^bula. 

The  Loixer  Extremity  is  usually  spinen  :f  as  the  External 
Malleolus.  It  i-  iir^cr  ir  :  n:  r-  pointed  than  the  upper  and 
is  indistinctiip  trimgiilar.  It  may  be  described  as  consisting  of 
internal  and  external  surfaces,  anterior  and  posterior  borders, 
and  an  apex.  The  outer  surface  is  prominent,  convex,  rough 
and  subcutaneous.  The  internal  surface  is  articular  through 
a  part  of  its  extent  :  mi  both  above  and  below  the  articular 
surface  is  found  2.  rinpitrned  space — that  above  for  the  inter- 
osseous ligaments  v,  nich.  i::nch  it  to  the  fibula,  that  below  for 


OSTEOLOGY.  49 

lig-amentous  fibres  binding-  it  to  the  foot.  The  articular  space 
is  intended  for  the  lateral  aspect  of  the  astragalus,  and  occa- 
sionally extends  upward  to  the  fibula.  The  posterior  border 
is  nearh'  straig-ht,  is  much  thicker  than  the  anterior  border, 
and  is  marked  by  a  shallow  g-roove  for  the  passag-e  of  tendons. 
The  (Ditcrior  border  is  narrow  and  convex,  and  slopes  obliquely 
from  above  downward  and  backward.  The  apex  is  a  blunt, 
roug"hened  point. 

The  Shaft  of  the  bone  is  twisted,  presenting"  what  is  known 
as  the  curve  of  torsion,  so  that  its  faces  and  borders  chang-e 
their  relative  positions  in  the  diiTerent  portions  of  the  bone. 
The  faces  ma}-  be  described  as  external,  internal,  and  posterior. 
The  external  face,  narrow  and  convex  above,  becomes  broader 
about  the  middle  of  the  bone,  and  owing-  to  the  twisting- 
of  the  bone  becomes  posterior  at  its  lower  one-third.  The 
internal  face,  slig-htly  curved  above,  marked  by  a  ridg-e 
over  the  central  portion  of  the  bone,  twists  at  the  lower 
third  to  become  anterior.  The  posterior  face,  narrow  and 
convex  above,  broader  and  still  convex  at  the  centre,  be- 
comes flat  and  internal  at  the  lower  one-third  of  the 
bone.  Of  the  borders,  the  anterior  is  slig-htly  marked  above, 
prominent  in  the  middle  of  the  bone,  divides  into  two  lines  at 
the  lower  one-third,  one  of  which  becomes  external  and  passes 
to  the  posterior  border  of  the  external  malleolus,  while  the 
other,  more  slig-htly  marked,  passes  to  the  anterior  border 
of  the  external  malleolus,  leaving-  between  them  a  triangular 
spaca,  which  is  a  continuation  of  the  internal  surface.  The 
external  border,  commencing-  at  the  head  of  the  bone,  much 
more  slightly  marked  than  the  internal  border,  becomes  posteri- 
or in  the  lower  third  of  its  course,  and  passes  to  the  back  of 
the  external  malleolus.  The  /;//6'r;/«/Z'('>r(^/rr  commences  at  the 
back  of  the  head  of  the  fibula,  becomes  the  interosseous  ridge 
in  the  middle  of  the  bone,  running  down  upon  the  internal  face, 
and  twists  to  the  front  of  the  bone  in  the  lower  portion  of  its 
course. 

The  Foot. 

The  Foot  bears  a  strong  resemblance  to  the  hand:  differing 
essentially  from  it  however  in  that  it  is  at  right  angles  to  the 

Deji  Anat— 4 


50  DESCRIPTIVE  ANATOMY. 

leg-;  and  consequently  its  surfaces  are  superior  and  inferior, 
instead  of  anterior  and  posterior.  It  consists  of  an  irregular 
set  of  bones  forming-  the  Tarsus,  a  set  of  long-  bones  forming- 
the  Metatarsus,  and  the  Phalang-es. 

The  Tarsus. 

The  Taisiis  consists  of  seven  bones:  The  Os  Calcis,  Astra- 
g-alus.  Scaphoid,  Cuboid,  and  three  Cuneiform  bones,  known 
as  E^xternal,  Middle,  and  Internal,  sometimes  as  First,  Second, 
and  Third.  These  bones  are  arrang-ed  in  two  rows:  the  first 
row,  or  posterior  row,  consisting- of  the  os  calcis  and  astrag-alus 
the  remaining-  five  bones  forming-  the  second  row. 

The  Bones  of  the  First  Row. 

The  Os  Calcis  (Iv.  Calx,  the  lieel)  forms  the  posterior  abutment 
of  the  arch  of  the  foot,  and  is  known  as  the  heel  bone.  It  pre- 
sents for  examination  two  extremities,  anterior  and  posterior, 
and  four  surfaces,  superior,  inferior,  and  two  lateral.  The 
upper  sicr/ace  consists  of  two  portions,  one  behind  the  other. 
The  posterior  one-half  of  the  upper  surface  is  roughened, 
marked  by  the  presence  of  a  few  nutrient  foramina,  and 
is  non-articular.  It  is  convex  from  side  to  side.  The 
anterior  portion  presents  two  articular  surfaces,  separated 
by  an  oblique  g-roove.  Of  these  surfaces,  the  larg-er  and  more 
posterior  is  convex  in  outline,  and  oblique  in  direction.  Its 
long  diameter  is  directed  from  before  downward  and  outward; 
and  it  corresponds  to  the  concave  receiving-  cavity  on  the  infe- 
rior surface  of  the  astragalus.  The  anterior  is  an  oblong 
articular  facet,  concave  from  above  downward  and  outward, 
the  direction  of  its  long  diameter  ;  and  intended  for  the  recep- 
tion of  the  convex  articular  facet  on  the  lower  surface  of  the 
astragalus.  The  groove  which  separates  the  two  surfaces  is 
called  the  Sulcus  Calcanei  (Iv.  THe  furrow  of  the  heel),  and  is 
directed  like  the  surfaces  :  that  is,  downward  and  outward. 
The  inferior  surface  is  rough,  narrow,  and  non-articular;  and 
presents  near  its  posterior  extremity  two  tuberosities,  of  which 
the  internal  is  the  larger.  The  anterior  part  of  the  inferior 
surface  is  hardly  more  than  a  rough  and  rounded  border.    The 


OSTEOLOGY.  51 

external  surface  is  convex  througfhout  its  course,  is  very  roug^h 
for  the  attachment  of  ligaments;  and  is  marked  by  two  gfrooves, 
one  above  the  other,  separated  by  a  slig-ht  roug-hened  ridg^e. 
These  g-oooves  are  intended  for  the  transmission  of  tendons. 
The  internal  surface  is  deeply  concave  ;  and  is  overhung-  in  its 
anterior  portion  by  a  projection  of  bone,  which  is  called  the 
sustentaculum  tali  (L.  A  support  for  the  ankle),  or  lesser 
■process  of  the  os  calcis.  The  deep  concavity  on  the  internal 
surface  is  caused  mainly  by  this  projection  of  bone,  which  is 
grooved  on  its  under  surface  for  the  transmission  of  a  tendon, 
and  which  bears  on  its  upper  surface  the  g-reater  portion  of 
the  anterior  one  of  the  two  facets  on  the  superior  face  of  the 
bone.  The  posterior  extremity  is  quadrilateral  in  outline, 
roug-h  at  its  lower  portion,  smooth  above  for  the  play  of  the 
bursa  between  itself  and  the  tendon  Achillis.  The  aiiterior 
extremity  is  concavo-convex,  forming-  a  saddle-shaped  articula- 
tion between  this  bone  and  the  cuboid.  This  surface  is  con- 
cave from  above  downward  and  outward,  convex  in  opposite 
direction. 

The  Astrag-ulus,  the  second  bone  of  the  first  row,  lies 
between  the  tibia  above,  the  two  malleoli  at  the  sides,  and 
the  OS  calcis  below.  It  presents  like  the  os  calcis  four  sur- 
faces and  two  extremities,  the  surfaces,  as  is  the  case  with  the 
OS  calcis,  being-  superior,  inferior,  and  two  lateral,  while  the 
extremities  are  anterior  and  posterior.  The  superior  surface 
is  divided  into  two  portions,  a  posterior  articular  portion,  and 
an  anterior,  frequently  called  the  "neck"  of  the  bone,  which  is 
non-articular.  The  articular  portion  is  narrow  behind  and  broad 
in  front,  a  fact  which  g-overns  some  of  the  movements  of  the 
ankle-joint.  It  is  composed  of  a  central  depression  with  two 
elevated  ridg-es,  one  upon  either  side,  or,  in  other  words,  it  is 
a  trochlear  surface.  The  inferior  surface  is  in  the  main  artic- 
ular, consisting-  of  two  facets.  The  posterior  facet  is  quadri- 
lateral and  concave,  its  long-  diameter  directed  downward  and 
outward  ;  and  corresponds  to  the  posterior  of  the  two  facets 
on  the  upper  surface  of  the  os  calcis.  The  anterior  articular 
facet  is  convex.  Its  long-  diameter  likewise  is  directed  down- 
ward and  outward  ;  and  it  corresponds  to  the  concave  facet  on 


52  DESCRIPTIVE  ANATONY. 

the  OS  calcls.  Between  these  two  articular  surfaces  is  a  deep 
oblique  g-roove,  running"  downward  and  outward,  which  is 
called  the  Sulcus  Tali.  This  sulcus  corresponds  in  position 
to  the  sulcus  calcanei ;  and  when  the  two  bones  are  articula- 
ted, the  junction  of  the  two  sulci  forms  a  canal,  which  is  known 
as  the  Sinus  Tarsi.  The  internal  face  is  articular  to  a  small 
extent ;  that  is,  at  the  junction  of  the  internal  and  superior 
faces  is  found  an  oblong-  articular  facet,  its  long-  diameter  di- 
rected from  before  backward,  continuous  with  the  articular 
surface  on  the  superior  face  of  the  bone,  and  intended  for  ar- 
ticulation with  the  internal  malleolus.  Below^  this  articular 
facet  is  a  rough  depression  for  ligamentous  attachment ;  and 
the  remainder  of  the  internal  surface  is  likewise  roug-hened. 
The  external  surface  is  triang-ular  or  pyriform,  the  base  up- 
ward and  apex  downward.  It  is  concave  from  above  down- 
ward, sHg-htly  convex  from  before  backward,  and  is  continu- 
ous with  the  articular  facet  on  the  superior  surface  of  the 
bone.  It  is  intended  for  articulation  with  the  external  mal- 
leolus. Below  the  articular  surface  is  a  slight  roug-hness  for 
ligamentous  attachment.  The  anterior  extremity,  or  head  of 
the  bone,  is  oval,  convex,  and  articular  ;  the  long  diameter  of 
the  head,  slightly  oblique  in  direction,  is  from  above  down- 
ward and  inward,  and  is  intended  for  articulation  with  the 
cavity  found  upon  the  scaphoid.  This  head  is  supported  upon 
a  constricted  portion  of  the  bone,  sometimes  called  the  "neck", 
a  part  of  which  has  been  already  seen  as  a  roughened  surface, 
in  front  of  the  articular  facet.  The  remaining  portion 
of  the  neck  is  rough  and  thick.  The  -posterior  extremity 
is  hardly  more  than  a  narrow  border.  It  is  marked  by  a  slight 
transverse  groove  just  behind  the  superior  articular  surface  ; 
and  by  an  oblique  groove,  which  extends  downward  and  in- 
ward, and  is  continuous  in  the  articulated  foot  with  the  concave 
inner  face  of  the  os  calcis. 

The  Bones  of  the  Second  Row. 

The  Cuboid  lies  between  the  os  calcis  behind,  the  scaphoid 
and  external  cuneiform  to  its  inner  side,  and  the  fourth  and 
fifth  metatarsal  bones  in  front.     It  presents  four  surfaces, 


OSTEOLOGY.  53 

superior,  inferior,  external,  and  internal,  and  an  anterior  and 
a  posterior  extremity.  The  upper  surface  looks  upward  and 
outward,  and  is  roug-h  and  irregular  for  the  attachment  of 
ligaments.  The  inferior  surface  is  very  irregular  in  outline.  A 
little  in  front  of  the  middle- it  is  divided  by  a  prominent  ridge, 
called  the  peroneal  ridg-e,  into  an  anterior  portion,  which  is 
occupied  almost  entirely  by  a  groove,  also  called  peroneal,  and 
a  larger  posterior  portion,  which  is  roughened  for  ligamentous 
attachment.  The  peroneal  ridge  terminates  externally  in 
the  tuberosity,  a  somewhat  rounded  blunt  projection  of  bone, 
which  constitutes  one  of  the  landmarks  of  the  foot.  The  in- 
ternal face  near  the  junction  of  the  inner  and  superior  faces  is 
marked  by  an  oblong  articular  facet,  which  is  intended  for 
articulation  with  the  external  cuneiform  bone.  Occasionally 
behind  this  facet  is  another  smaller  facet  for  articulation  with 
the  scaphoid,  though  usually  these  bones  do  not  articulate  with 
one  another.  Below  the  articular  facet  the  bone  is  rough  for 
the  attachment  of  the  interosseous  ligaments.  The  external 
face  is  in  reality  only  a  border.  It  is  narrow  and  rough- 
ened, presenting  the  projection  of  the  peroneal  ridge  and  the 
commencement  of  the  peroneal  groove.  The  anterior  extrem- 
ity is  divided  into  two  articular  facets  by  a  vertical  ridge. 
The  inner  of  these  facets  is  quadrilateral  in  outline;  the  external, 
triangular.  They  are  intended  for  articulation  with  the  fourth 
and  fifth  metatarsal  bones  respectively.  The  posterior  ex- 
tremity is  concavo-convex,  being  concave  from  above  downward 
and  inward  and  convex  from  within  outward,  to  correspond  with 
a  similar  articular  surface  on  the  anterior  extremity  of  the  os 
calcis.  At  the  junction  of  the  inferior  and  internal  surfaces 
tl.is  extremity  is  prolonged  backward  and  inward,  so  that 
the  OS  calcis  apparently  rests  partly  upon  a  prolongation  of 
the  cuboid. 

The  Scaphoid,  the  second  bone  of  this  row,  presents  an 
anterior  posterior,  superior,  and  inferior  surface  ;  and  in- 
ternal and  external  extremities.  The  posterior  surface  is 
entirely  occupied  by  a  concave  smooth  articular  facet,  whose 
transverse  diameter  is  greater  than  its  vertical,  and  is  intended 


54  DESCRIPTIVE  ANATOMY. 

for  articulation  with  the  head  of  the  astragalus.  The  anterior 
surface  has  three  articular  facets,  separated  by  two  slig-htly- 
marked  vertical  ridg-es.  These  facets  articulate  with  the  three 
cuneiform  bones.  The  most  internal,  which  approaches  the 
nearest  to  the  inferior  surface  of  the  bone,  is  large  and  slight- 
ly triangular;  the  central,  quadrilateral;  and  the  external,  also 
nearly  quadrilateral  in  outline,  is  oblique  in  its  direction. 
Thtszcj)e7'ior surface  \^  convex  from  side  to  side;  and  roughened 
for  ligamentous  attachment.  The  inferior  surface,  narrower 
than  the  superior,  is  also  roughened  for  ligamentous  attach- 
ment. The  inner  extremity  of  the  bone  is  a  blunt  projection, 
the  tuberosity  of  the  Scaphoid  which,  with  the  tuberosity  of  the 
internal  cuneiform,  furnishes  another  of  the  landmarks  of  the 
foot.  The(9«/er  extremity  is  usually  roughened;  but  occasion- 
ally presents  a  small  facet  for  articulation  with  the  cuboid. 

The  Internal  Cuneiform,  like  the  other  two,  is  irregularly 
wedge-shaped ;  and  lies  on  the  inner  side  of  the  tarsus, 
between  the  first  metatarsal  in  front,  the  scaphoid  behind, 
and  the  middle  cuneiform  and  second  matatarsal  to  the 
outer  side.  It  is  the  largest  of  the  cuneiform  bones;  and 
unlike  all  of  the  others,  is  broader  below  than  above. 
Its  internal  face  is  rough  and  convex.  The  external  face 
is  marked  along  the  junction  of  the  superior,  external  and 
posterior  faces  by  a  reversed  L-shaped  facet,  intended  for 
articutation  with  the  middle  cuneiform.  In  front  of  this 
facet  is  a  smaller  articular  surface  for  the  second  metatarsal 
bone.  The  ■posterior  face  is  concave,  slightly  triangular  in 
outline,  corresponding  to  the  internal  one  of  the  facets  upon 
the  scaphoid.  The  anterior  face  is  articular  throughout, 
slightly  convex,  and  is  said  to  be  kidney-shaped.  The  inferior 
face,  or  base  of  the  bone,  is  very  rough  ;  and  terminates  pos- 
teriorly in  the  blunt  elevation  or  tuberosity  of  the  internal 
cuneiform.  The  superior  face  is  scarcely  more  than  a  rough 
narrow  border. 

The  Middle  Cuneiform  lies  between  the  internal  cunei- 
form on  its  inner,  and  the  external  cuneiform  on  its  outer 
side,  the  scaphoid   bone  and   the  second   metatarsal  in  front. 


OSTEOLOGY.  55 

Its  superior  surface,  much  broader  than  its  inferior,  is  roug-h 
and  irreg"ular  for  the  attachment  of  lio-aments.  The  inferior 
surface,  scarcely  more  than  a  border,  is  also  roug^hened.  The 
iuterual  surface  presents  a  reversed  Iv-shaped  facet  similar  to 
the  one  found  upon  the  internal  cuneiform.  The  exter- 
nal surface  has  an  articular  facet  upon  its  posterior  portion  ; 
but  is  non-articular  in  front,  being-  roug-hened  for  the  attach- 
ment of  the  interosseojus  ligament.  The  posterior  surface  is 
smooth,  slightly  quadrilateral  in  outline  for  articulation  with 
the  middle  facet  upon  the  scaphoid.  The  anterior  surface  is 
articular,  convex  slig"htly  from  side  to  side  for  articulation 
with  the  base  of  the  second  metatarsal  bone.  This  bone  is 
more  distinctly  wedg-e-shaped  than  the  other  two  cuneiform 
bones. 

The  External  Cuneiform  is  intermediate  in  size  between 
the  internal  and  the  middle.  It  lies  with  the  middle  cunei- 
form to  its  inner,  and  the  cuboid  to  its  outer  side,  the 
scaphoid  behind  and  the  third  metatarsal  bone  in  front. 
The  bone  appears  to  be  slig"htly  bent  upon  itself,  so  as  to  be 
concave  internally  and  convex  externally.  Its  superior  sur- 
face is  roughened  like  the  preceding*  tarsal  bones  ;  its  infe- 
rior surface,  narrower  than  the  superior,  is  likewise  rough 
for  lig-amentous  attachment.  The  internal  surface  is  slightly 
concave  from  before  backward  ;  and  presents  an  articular 
facet  near  its  posterior  end  for  articulation  with  the  middle 
cuneiform.  In  front  of  this  facet  it  is  roughened  for  the 
interosseous  ligfament.  Near  the  anterior  extremity  is  a 
very  slight  facet  for  articulation  with  the  lateral  aspect  of  the 
second  metatarsal  b^ne.  The  exteriial  surface  has  an  oblong 
facet  near  its  upper  posterior  portion,  corresponding"  to  the 
slight  facet  which  is  found  on  the  inner  face  of  the  cuboid.  In 
front  of  this  the  external  surface  is  roug-hened  for  lig*amentous 
attachment.  Posteriorly  it  presents  a  smooth,  nearly  flat  ar- 
ticular facet,  which  is  cut  ol>li(]uelyv,u  as  to  face  backward  and 
inward,  thus  disting-ui.shing-  it  from  the  other  cuneiform  bones, 
whose  posterior  extremities  are  cut  squarely.  The  anterior 
surface,  or  extremity,  presents  a  smooth  quadrilateral  articu- 
lar facet  for  articulation  with  the  third  metatarsal  bone. 


56  DESCRIPTIVE  ANATOMY. 


The  Metatarsal  Bones. 

The  Metatarsal  Bones  present  the  same  g-eneral  charac- 
teristics as  the  metacarpal.  They  are  long-  bones,  pre- 
senting" a  shaft  and  two  extremities.  Like  the  metacarpal 
bones  they  are  five  in  number  ;  but  are  numbered  from  within 

outward . 

A  Typical  Metatarsal  Bone. 

A  Typical  Metatarsal  Bone  presents  a  posterior  extremity, 
or  base,  an  anterior  extremity,  or  head,  and  a  shaft.  The 
posterior  extremity  is  quadrilateral  in  outline,  marked  by  an 
articular  facet  upon  its  summit,  and  an  articular  facet  upon  each 
lateral  aspects,  its  superior  and  inferior  surfaces  being-  roug-h 
and  square.  Its  head,  much  smaller  than  its  base,  presents  on 
its  summit  an  articular  facet,  which  is  convex,  with  its  long- 
diameter  vertical.  Behind  the  head  is  a  slightly  constricted 
portion,  which  is  surmounted  on  each  side,  near  the  dorsal 
aspect  of  the  bone,  by  a  well-marked  tubercle,  while  a  smaller 
tubercle  is  found  near  the  plantar  aspect.  Near  the  plantar 
aspect  the  head  is  grooved  for  the  transmission  of  tendons. 
The  shaft  of  the  bone  is  narrow  ;  and  presents  a  dorsal  sur- 
face marked  by  an  indistinct  ridge,  bifurcating  below  to 
extend  to  the  two  dorsal  tubercles.  The  lateral  surfaces  are 
concave,  so  as  to  leave  an  interosseous  space  between  the 
adjoining  metatarsal  bones  ;  and  the  inferior  border  is  rounded 
and  indistinctly  marked. 

The  First  metatarsal  bone  is  very  massive.  Its  poste- 
rior extremity  presents  a  concavo-convex  articular  surface  ; 
and  its  anterior  extremity,  presenting  a  rounded  head,  is,  un- 
like the  other  metatarsal  bones,  nearly  as  larg-e  as  the  posterior 
extremity. 

The  Second  metatarsal,  the  longest  of  the  metatarsal 
bones,  presents  an  articular  facet  on  its  summit  for  the 
middle  cuneiform,  on  its  inner  side  an  articular  facet  for 
the  internal  cuneiform,  and  on  its  outer  side  a  well-marked 
articular  facet  for  the  third  metatarsal,  and  a  somewhat 
slightly  marked  facet  for  the  external  cuneiform. 


OSTEOLOGY.  57 

The  Third  metatarsal  bone  presents  an  articular  facet 
on  either  side,  that  on  the  inner  side  being-  divided  into  two  by 
an  antero-posterior  g-roove.  On  its  summit  is  an  articular 
facet  for  the  external  cuneiform  bone. 

The  Fourth  metatarsal  is  the  typical  metatarsal  bone ; 
and  need  be  no  further  described. 

The  Fifth  metatarsal  bone  has  as  its  peculiar  character- 
istic a  blunt  projection  on  the  outer  side  of  its  base,  this 
projection  being-  subcutaneous,  and  one  of  the  most  important 
landmarks  of  the  foot.     It  has  only  one  lateral  articular  facet. 

Certain  g-eneral  characteristics  enable  us  to  distinguish 
between  the  metatarsal  and  metacarpal  Ijones.  The  most  im- 
portant is  that  the  metatarsal  bones  are  all  about  the  same 
length,  but  are  slenderer  than  the  metacarpal ;  and  whereas 
in  the  metacarpal  bones  the  head  is  always  of  nearly  the  same 
or  greater  size  than  the  base,  in  the  metatarsal  bones  the  base 
more  than  doubles  the  size  of  the  head,  with  the  sing-le  excep- 
tion of  the  first  metatarsal,  which  is  disting-uished  by  other 
marks. 

The  Phalanges. 

The  Phalang-es  of  the  toes,  like  those  of  the  fingers, 
are  arrang-ed  in  three  rows,  except  that  the  great  toe  has,  like 
the  thumb,  but  two  phalang-es,  the  place  of  the  second  being- 
taken  by  the  ungual.  They  resemble  those  of  the  hand  soclosely 
that  a  separate  description  is  not  necessary.  They  are  smaller 
and  shorter  than  those  of  the  hand,  the  second  phalanx  partic- 
ularly being  scarcely  more  than  a  neck  of  bone  separating-  two 
articular  extremities,  while  the  ungual  phalanx  is  frequently 
scarcely  distinguishable,  except  that  for  the  first  toe.  In  the 
fifth,  or  little  toe  the  ungual  and  second  phalanges  are  some- 
times found  ossified  together. 

The  Skeleton  of  the  Head. 

The  skeleton  of  the  head,  or  skull,  consists  of  two'portions, 
the  bones  of  the  cranium  and  those  of  the  face. 

Cranium. 

The  cranium  is  the  upper  posterior  division  of  the  skull,  and 
is  formed  by  the  union  of  eight  bones — occipital,  frontal,  sphe- 


58  DESCRIPTIVE  ANATOMY. 

noid,  ethmoid,  two  parietal  and  two  temporal.  These  become 
securely  ossified  tog-ether  in  mature  life,  and  can  be  separated 
only  in  the  young-  subject. 

Occipital. 

The  occipital  bone, sometimes  called  the  first  cranial  vertebra, 
is  situated  at  the  posterior  part  of  the  cranium,  and  presents 
for  examination  two  surfaces,  four  ang-les  and  four  borders. 

The  posterior  surface,  frequently  erroneously  called  exter- 
nal, is  convex,  and  presents  above  its  centre  an  eminence  called 
the  posterior  occipital  protuberance  ;  curving  outward  from 
this  on  either  side  is  a  roug-h  ridg-e  called  the  superior  curved 
line  ;  passing-  downward  from  the  protuberance  to  a  large 
aperture — the  foramen  magnum — is  a  sharp  ridge,  the  occipital 
crest ;  arching  outward  on  either  side  from  the  middle  of  the 
crest,  and  concentric  with  the  superior  curved  line  is  the  infe- 
rior curved  line.  The  portion  between  the  curved  lines  is 
slightly  depressed  and  rough.  At  the  lower  termination  of 
the  crest  is  seen  the  foramen  magnum,  a  large  oval  opening, 
whose  antero-posterior  diameter  is  the  longer  and  whose 
larger  end  is  behind.  On  either  side  of  the  front  half  of  the 
foramen  magnum  is  seen  the  condyle  for  articulation  with  the 
superior  articular  process  of  the  atlas  ;  it  is  oval,  convex, 
articular,  and  directed  obliquely  forward  and  inward.  Just 
behind  the  condyle  is  a  depression,  the  posterior  condyloid 
fossa,  with  occasionally  a  foramen  opening  into  it — the  poste- 
rior condyloid  foramen.  In  front  of  the  condyle  is  the  anterior 
condyloid  foramen.  Passing  outward  from  the  condyle  is  a 
rounded  elevated  ridge,  the  transverse  process.  On  the  inner 
aspect  of  the  condyle  is  a  tubercle.  In  front  of  the  foramen 
magnum  is  the  basilar  process  ;  it  is  horizontal,  quadrilateral, 
convex,  and  presents  an  antero-posterior  ridge,  the  pharyn- 
geal spine. 

The  anterior  face  is  concave  and  presents  four  ridges,  meet- 
ing at  right  angles,  about  the  middle,  called  the  crucial  ridge, 
or  occipital  cross.  E)ach  ridge  is  called  an  arm  of  the  cross. 
Three  of  these  ridges  are  grooved  ;  while  the  fourth,  which  is 
the  inferior,  is  sharp  and  not   grooved  until   it  approaches  the 


y 


\ 


OSTEOLOGY.  59 

foramen  mag"nuiii.  At  the  point  where  the  four  arms  meet 
there  is  an  eminence  called  the  anterior  occipital  protuberance. 
Above  each  lateral  arm  of  the  cross  there  is  a  shallow  depres- 
sion, the  cerebral  fossa  ;  below  each  lateral  arm  is  another 
depression,  the  cerebellar  fossa.  At  the  termination  of  the 
lower  arm  is  the  foramen  mao-num,  and  on  each  side  of  this 
the  anterior  condyloid  foramen.  In  front,  and  to  each  side  of 
the  foramen  majs^num  is  a  smooth  broad  groove  for  the  termi- 
nation of  the  lateral  sinus.  In  front  of  the  foramen  mao-num 
is  the  basilar  process,  which,  as  on  its  inferior  surface,  is 
nearly  horizontal  and  quadrilateral,  but  is  here  concave  to  sus- 
tain the  medulla  oblong-ata. 

The  ang-les  are  superior,  inferior  and  two  lateral.  The 
lateral  ang-les  are  each  situated  where  the  g-roove  in  the  lateral 
limb  of  the  crucial  ridg-e,  strikes  the  border  of  the  bone.  The 
inferior  angle  is  the  truncated  extremity  of  the  basilar  process, 
and  articulates  w^ith  the  body  of  the  sphenoid. 

The  superior  ang"le  juts  into  the  interval  formed  by  the  union 
of  the  posterior  superior  angfles  of  the  parietal  bones. 

The  borders  are  two  superior  and  two  inferior,  l^ach 
superior  border  is  serrated  for  articulation  with  the  parietal 
bone  ;  and  extends  from  the  superior  to  the  lateral  angle. 

Each  inferior  border  articulates  with  the  temporal  bone, 
mastoid  and  petrous  portions  ;  is  serrated  below  the  lateral 
angle  and  is  interrupted  about  its  middle  by  a  protuberance, 
the  jugular  eminence,  in  front  of  which  is  a  depression,  the 
jug*ular  fossa. 

Parietal. 

The  two  parietal  bones  form  the  upper  and  most  of  the  lat- 
eral wall  of  cranium,  and  are  situated  between  the  frontal  and 
occipital  bones,  in  front  and  behind,  and  the  two  temporal 
bones  laterally.  Each  bone  is  divided  into  tuo  snrfaccs,  four 
borders,  3.nd  Jhur  cDi^i^lcs.  The  cxlcrnal  surface  is  convex  and 
presents  a  decided  bulg-e  about  the  middle,  the  parietal  emi- 
nence ;  through  this  is  seen  running  the  temporal  ridg-e,  arch- 
ing across  this  bone  from  the  frontal  ;  below  the  ridge,  is  a 
nearly  flat  surface  forming-  part  of  the  temporal  fossa.     Near 


60  DESCRIPTIVE  ANATOMY. 

the   posterior    superior   ang-le    is    seen  the  parietal   foramen, 
which  is  frequently  absent. 

The  internal  surface  is  mostly  concave  and  is  sunken  in  the 
middle  into  a  fossa.  It  is  marked  by  dig-ital  pits  for  lodging- 
cerebral  convolutions,  and  the  arborescent  furrows  worn  by 
the  arteries.  Along-  the  edg-e  of  the  superior  border  is  seen 
half  of  a  g-roove,  completed  by  the  opposite  bone,  and 
formed  by  the  long-itudinal  sinus. 

The  borders  are  four.  The  anterior,  for  articulation  with 
the  frontal  bone,  and  the  -posterior,  for  the  occipital,  are  serra- 
ted. The  superior  border,  for  articulation  with  its  fellow, 
straig-ht,  serrated  and  thick.  The  inferior  border,  for  articu- 
lation with  the  squamous  portion  of  the  temporal  bone,  is  short, 
curved  and  beveled  at  the  expense  of  the  outer  table.  The 
ang-les  are  four.  The  anterior  superior  and  the  posterior  supe- 
rior are  rig-ht  angles.  The  anterior  inferior  is  long-,  thin  and 
marked  on  its  inner  aspect  by  a  furrow  formed  by  the  middle 
mening-eal  artery.  '^\^t  posterior  Inferior  is  blunt  and  usually 
marked  internally  by  the  g-roove  for  the  lateral  sinus. 

Frontal. 

The  frontal  bone  is  situated  at  the  front  and  base  of  the  cra- 
nium. In  early  life  the  bone  consists  of  symmetrical  lateral 
halves,  separated  by  a  vertical  suture,  which,  however,  be- 
comes ossified  later  in  life,  though  the  bone  could  still  be  de- 
scribed as  consisting-  of  two  similar  lateral  portions.  The 
bone  is  described  as  being-  made  up,  in  each  of  its  lateral 
halves,  of  two  portions — the  vertical,  or  frontal,  and  the  hori- 
2;ontal,  or  orbito-nasal  portion. 

The  vertical  portion  forms  the  skeleton  of  the  forehead  and 
presents  two  surfaces  and  a  lateral  aspect.  Upon  the  anterior 
surface,  which  is  convex,  there  are  seen  superiorly  a  smooth, 
somewhat  flattened  surface ;  below  this  a  bulg-e,  called  the 
frontal  eminence  ;  below  this  a  broad,  shallow,  transverse 
g-roove  ;  below  this  a  transverse  ridge,  the  superciliary  ;  be- 
tween this  and  the  opposite  ridg-e,  on  the  middle  line,  is  a 
prominence  called  the  g-labella,  or  nasal  tuberosity.  Below 
the  superciliary  ridg-e  is  seen  the  marg-in  of  the  orbit,  called 


OSTEOLOGY.  61 

the  supra-orbital  ridg-e,  which  terminates  at  the  inner  extremity 
in  the  internal  ang-ular  process,  and  at  its  outer  in  the  external 
angular  process.  About  the  inner  third  of  the  supra-orbital 
rldg-e  is  a  notch,  sometimes  formei  into  a  foramen,  called  the 
supra-orbital  notch  or  foramen. 

The  posterior  face  of  the  vertical  portion  is  concave  and 
marked  by  digital  pits  and  arborescent  furrows  for  the  arte- 
-riesr-^n  the  middle  line  this  surface  presents  superiorly  a 
g-roove  for  the  longitudinal  sinus,  which,  as  it  descends,  termi- 
nates in  a  ridge,  at  the  extremity  of  which  is  a  small  foramen, 
called  the  foramen  coecum. 

The  lateral  aspect  of  the  bone  presents  a  ridge  curving  up- 
ward and  backward  from  the  external  angular  process,  and 
called  the  temporal  ridge  ;  behind  this  the  surface  is  sunken 
and  forms  part  of  the  temporal  fossa.  Both  the  temporal  ridge 
and  fossa  are  only  j)artially  seen  on  the  frontal  bone,  for,  in 
the  articulated  skull,  they  are  continued  on  to  the  parietal  and 
temporal  bones. 

The  horizontal  portion  consists  of  two  lateral  parts,  the 
orbital  plates,  separated  by  a  rectangular  notch,  the  ethmoidal 
fissure.  Each  orbital  plate  presents  an  inferior  and  a  superior 
surface.  The  inferior  face  is  smooth,  triangular  and  concave, 
the  concavity  being  greatest  behind  the  external  ang-ular 
process — the  lachrymal  fossa.  It  has,  just  within  the  supra 
orbital    notch,    a    depression    called    the   fovea    trochlearis. 

The  upper  surface  of  the  orbital  plate  is  convex  and  rough, 
presenting  irregular  rough  eminences. 

The  ethmoidal  fissure,  the  margins  of  which  present  several 
half  cells,  which,  when  articulated  with  the  ethmoid,  complete 
theethmoidal  cells,  is  the  rectangular  notch  separating  the 
two  orbital  plates. 

In  front  of  it  is  a  roughened  interval,  between  the  two 
internal  angular  processes,  called  the  nasal  notch,  descend- 
ing from  the  middle  of  which  is  a  long  pointed  process, 
the  nasal  spine.  Upon  the  posterior  surface  of  the  nasal 
spine  is  a  vertical  ridge.  In  the  front  portion  of  the  ethmoidal 
notch  and  external  to  the  nasal  spine,  are  the  openings  of  the 


62  DESCRIPTIVE  ANATOMY. 

frontal  sinuses.  The  frontal  sinus,  one  on  each  side  of 
the  middle  line,  is  an  irreofular  cavity  between  the  two  tables 
of  the  vertical  portion  which  gradually  increase  in  size  from 
the  time  it  makes  its  appearance  in  early  life. 

The  borders  of  the  frontal  bone  are  two — ^superior  and 
inferior.  The  siirperior  border  is  semi-circular  and  serrated 
for  articulation  with  the  parietal  bones.  When  examined  closely 
it  is  seen  to  be  beveled  superiorly  at  the  expense  of  the  inner 
table,  and  interiorly  at  the  expense  of  the  outer. 

ThezVz/dT/or  border  is  the  posterior  termination  of  the  orbital 
plates,  interrupted  in  the  middle  by  the  ethmoidal  notch.  It 
is  straig-ht  and  articular  with  the  lesser  wing-  of  the  sphenoid. 
At  the  ang-le  of  the  junction  of  the  two  borders,  there  is  a 
rough  triangular  surface,  the  sphenoidal  triang-le,  for  articu- 
lation with  the  greater  wing  of  the  sphenoid. 

Temporal  Bone. 

The  temporal  bone  is  divided  for  stud}'-  into  the  squamous, 
mastoid  and  petrous  portions. 

The  squamous  -portion  occupies  the  upper  front  part  of  the 
bone  and  consists  of  two  surfaces,  a  semi-circular  border  and 
a  projection  called  the  zygoma.  The  internal  surface  is  con- 
cave from  above  downward  and  from  before  backward.  It  is 
marked  by  irregular,  antero-posterior  elevations  with  inter- 
vening depressions  for  the  convolutions  and  sulci  of  the  brain. 
No  distinct  line,  in  the  adult,  marks  the  point  of  separation 
between  the  squamous  and  petrous  portions.  The  external 
surface  may  be  conveniently  divided  into  two'^parts — that 
which  lies  above  and  that  which  lies  below  the  zygoma.  The 
part  above  is  convex  from  above  downward,  slightly  concave 
from  before  backward,  rough  for  muscular  attachment  and 
enters  into  the  formation  of  the  temporal  fossa.  Posteriorly 
it  is  separated  from  the  mastoid  portion  by  a  rough  line, 
part  of  the  temporal  ridge.  The  rest  of  this  surface  is  occu- 
pied by  the  zygoma  and  the  glenoid  cavity. 

The  zygoma,  or  zygomatic  process,  at  its  origin  from 
the  squamous  portion,  passes  outward  with  a  slight  in- 
clination   forward;    but   after   a   course   of   about  one-fourth 


OSTEOLOGY.  63 

of  an  inch,  is  twisted  upon  itself  so  that  the  surfaces 
and  borders  change  their  relative  positions.  At  its  orig-in 
the  surfaces  are  superior  and  inferior,  the  first  occupied 
by  a  g-roove,  the  second  b}'  a  roughened  tubercle  ;  but 
in  the  remainder  of  its  course,  where  it  passes  forward 
with  but  a  slight  inclination  outward,  the  surfaces  become 
internal  and  external,  the  borders  superior  and  inferior.  The 
external  surface  is  rough,  convex  both  from  above  downward 
and  from  before  backward.  The  internal  surface  is  concave 
in  both  directions  and  smooth.  The  superior  border  is  longer, 
thinner  and  sharper  than  the  inferior,  which  is  thick  and 
rough  and  short.  Anteriorly  it  terminates  in  a  rough 
serrated  extremity,  obliquely  cut  from  above  downward  and 
backward,  and  intended  for  articulation  with  the  malar.  Pos- 
teriorly, the  zygoma  rises  by  two  rough  lines  called  the  roots 
of  the  zygoma.  The  anterior  root  is  continuous  with  the  in- 
ferior border  and  terminates  in  a  rough  projection  called  the 
tubercle  of  the  zygoma,  from  which  a  smooth  elevated  ridge, 
the  eminentia  articularis,  passes  inward  as  the  anterior  bound- 
ary of  the  glenoid  cavity.  The  posterior  root  passes  back- 
ward, just  above  the  glenoid  cavity  and  the  external  auditory 
meatus,  and  than  curving  upward  forms  the  continuation  of 
the  temporal  ridge  which  separates  the  squamous  from  the 
mastoid  portion.  Just  after  it  passes  above  the  gdenoid  cavity, 
it  sends  downward  a  prominent  articular  projection,  sometimes 
called  the  middle  root  of  the  zygoma,  which  forms  the  poste- 
rior boundary  of  the  articulation  for  the  lower  jaw. 

Tho.  fylenoid  cavily  \'i  concave  and  oval  in  outline,  its  long 
diameter  being  directed  from  without  back  weird  and  inward. 
it  is  bounded  in  front  by  the  eminentia  articularis,  a  smooth, 
rounded,  oval  articular  ridge  which  is  a  continuation  of  the 
anterior  root  of  the  zygoma.  Posteriorly  it  is  limited  by  a 
rough,  quadrilateral  sheet  of  bone  called  the  tympanic  plate, 
while  in  the  middle  is  a  well  defined  slit,  the  Glaserian  fissure, 
which  divides  the  cavity  into  an  anterior  articular  portion  and 
a  posterior  non-articular.  The  articular  portion  is  limited  be- 
hind by  the  middle  root  of  the  zygoma,  sometimes  called  the 
post-glenoid  tubercle. 


64  DESCRIPTIVE  ANATOMY. 

The  semi-circular  border  is  roug-h,  thin  and  sharp  above, 
strong-ly  beveled  at  the  expense  of  the  inner  table  ;  thick  and 
serrated  below  and  slightly  beveled  at  the  expense  of  the  outer 
table. 

The  Mastoid  portion  consists  of  an  internal  and  external 
surface  ;  superior  and  posterior  borders  and  a  roug-h  nipple 
like  projection,  the  mastoid  process.  The  interned  surface 
presents  but  one  mark  of  note.  It  is  smooth  and  has  a  deep 
g-roove  which  runs  from  above  downward  and  backward.  It 
is  called  the  fossa  sigmoidea.  The  external  surface  is  roug-h 
throughout  and  presents  near  the  posterior  border  a  larg-e 
foramen,  called  the  mastoid,  which  is  sometimes  found  in  the 
suture  between  this  bone  and  the  occipital  and  sometimes  is 
altog-ether  wanting. 

The  Mastoid  process  is  a  roug-h,  blunt  projection  of 
bone,  marked  internally  by  a  deep  g-roove,  the  dig-astric 
fossa,  internal  to  which  is  a  shallower  g-roove  for  the  occipital 
artery  and  known  as  the  occipital  g-roove.  The  interior 
of  the  mastoid  portion  is  hollowed  out  into  a  number  of  cellular 
cavities.  The  superior  border  is  roug-h,  serrated  and  nearly 
straig-ht  to  receive  the  posterior  inferior  ang-le  of  the  parietal. 
The  -posterior  border,  longer  than  the  superior,  slopes  from 
above  downward  and  forward  and  is  roughened  for  articula- 
tion with  the  occipital. 

The  Petrous  portion  is  a  pyramidal  projection  of  bone  with 
its  apex  directed  inward  and  forward  and  its  base  outward 
and  backward.  It  presents  three  surfaces,  anterior  posterior 
and  inferior  ;  and  three  borders,  superior,  anterior  and  pos- 
terior. The  -posterior  surface  is  the  simplest  of  the  three. 
Internal  to  its  middle  point  it  presents  an  oblique  oval  open- 
ing, the  internal  auditory  meatus.  This  opening  leads  into  a 
short  canal,  directed  outward  and  forward,  at  the  bottom  of 
which  may  be  seen  a  bony  lamina  perforated  by  numerous 
apertures  and  crossed  by  a  transverse  ridge.  E^xternal  to  the 
internal  auditory  meatus  and  near  the  posterior  border,  is  seen 
a  little  slit  like  aperture  which  leads  to  the  acqueductus  vesti- 
buli.     Between  the  two,  and  near  the  superior  border,  is  usu- 


OSTEOLOGY.  65 

ally  seen  a  slig-hter  depression   which  lodg-es  a  process  of  the 
dura  mater. 

The  anterior  surface  presents  near  the  middle  a  round 
elevation  which  marks,  the  position  of  the  superior  semi- 
circular canal  ;  external  to  this  a  smooth  concave  surface 
forms  the  roof  of  the  tympanum  ;  below  and  in  front  of  the 
bulg-e  is  a  groove  leading-  outward  and  backward  to  an  open- 
ing-, the  hiatus  Fallopii,  while  at  the  junction  of  the  squamous 
and  petrous  portions  may  sometimes  be  seen  another  and  slig-hter 
groove,  the  petrosal.  Near  the  apex  of  the  bone  is  seen  a  de- 
pression for  the  Gaserian  g-anglion,  while  at  the  apex  the 
roof  of  the  carotid  canal  is  usually  wanting-  and  a  part  of  the 
canal  may  be  seen  from  the  anterior  surface. 

The  inferior  surface  is  roug-h  and  irreg-ular  and  has  upon  it 
eleven  points  which  require  examination.  Near  the  apex  of 
the  bone  is  a  roug-h,  nearly  quadrilateral  surface  which  g-ives 
attachment  to  muscular  fibres.  External  to  this  is  a  circular 
opening-,  the  aperture  of  entrance  of  the  carotid  canal.  At 
first  this  canal  passes  upward  in  the  bone,  but  it  abruptly 
turns  forward  and  inward  and  downward,  pursuing-  a  course 
parallel  with  that  of  the  petrous  bone,  to  emerg-e  at  the  apex. 
External  and  slightly  behind  this  is  a  smooth,  concave  surface, 
which  encroaches  on  the  posterior  border  of  the  bone,  called 
the  jugfular  fossa.  On  the  bony  partition  separating-  the  jug-u- 
lar  fossa  from  the  carotid  aperture,  is  a  small  foramen  which 
transmits  Jacobson's  nerve  :  and  on  the  outer  wall  of  the  fossa 
itself  is  another  foramen,  smaller  in  size,  for  Arnold's  nerve. 
Behind  and  slig-htly  internal  to  the  carotid  aperture,  near  the 
posterior  border  and  directly  beneath  the  internal  auditory 
meatus,  is  a  small  opening",  the  aqueduct  of  the  cochlea.  Exter- 
nal and  anterior  to  the  carotid  aperture,  is  a  thin,  prominent 
tong-ue  of  bone,  which  extends  outward  to  become  continuous 
with  the  auditory  process,  called  the  vag-inal  process.  At  its 
base  this  process  splits  into  two  sheets,  one  in  front  of  the 
other,  to  enclose  a  sharp  pointed  projection,  the  styloid  pro- 
cess. This,  the  long-est  of  such  processes  in  the  body,  passes 
downward  and  slig-htly  forward  and   outward.     Behind  and 

Des  Anat — 5 


66  DESCRIPTIVE  ANATOMY. 

external  to  this  is  a  larg-e  foramen  in  the  bone,  the  stylo- 
mastoid ;  while  between  the  vag-inal  process  and  the  mastoid 
process  is  a  slig"ht  g-roove,  the  auricular  fissure.  At  the  junc- 
tion of  the  posterior  border  of  the  mastoid  portion  with  that  of 
the  petrous  portion,  there  is  a  rough  articular  surface  called 
the  jugfular  facet. 

The   borders  are  three,   superior,   -posterior  and   anterior. 

The  superior  border,  the  longest  of  the  three,  presents 
along  its  upper  margin  a  groove  for  the  petrosal  sinus,  and 
near  the  apex  of  the  bone  a  nptch  to  lodge  the  fifth  cranial 
nerve.  '^\\^ posterior  border,  intermediate  in  length,  usually 
presents  near  its  middle  a  rough  tongue  of  bone  which  divides 
the  jugular  fossa  into  two  portions.  The  remainder  of  the 
border  is  rough  for  articulation  w^ith  the  basilar  process  of  the 
occipital.  The  anterior  border  is  the  shortest  of  the  three, 
and  is  in  part  articular  for  the  greater  wing  of  the  sphenoid. 
In  the  receding  angle  between  the  petrous  and  squamous 
portions  there  is  seen  an  irregular  opening,  divided  into  an 
upper  and  a  lower  portion  by  a  thin  shelf  of  bone  known  as  the 
processus  cochleariformis.  The  canal  above  this  shelf  is  for 
the  tensor  tympani  muscle  while  that  below  is  intended  for  the 
Kustachian  tube. 

The  base  of  the  petrous  portion  is  partly  interposed  between 
the  other  two  portions  and  partly  continuous  with  them.  On 
the  free  portion  is  seen  the  opening  into  the  ear,  the  external 
auditory  meatus,  which  is  situated  between  the  mastoid  process 
behind  and  the  middle  root  of  the  zygoma  in  front,  and  between 
the  posterior  root  of  the  zygoma  above  and  the  auditory  process 
below.  The  auditory  process  is  a  rough  curved  sheet  of  bone 
continuous  with  the  vaginal  process,  and  partly  circumscribing 
the  external  auditory  meatus. 

The  apex  of  the  petrous  portion  is  rough  and  presents  a  large 
irregular  aperture,  the  aperture  of  exit  for  the  carotid  artery. 
It  is  received  between  the  basilar  process  of  the  occipital  bone 
and  the  spinous  process  of  the  sphenoid. 

The  Sphenoid. 

The  sphenoid  occupies  a  position  near  the  middle  of  the  base 
of  the  skull,  and  maybe  considered  the  key-stone  of  the  cranial 


OSTEOLOGY.  67 

arch,  since  it  serves  to  bind  tog; ether  all  the  bones  of  the  skull 
and  five  of  those  of  the  face.  It  has  been  likened  to  a  bat  with 
the  wing's  spread  out,  and  is  divided  for  study  into  a  bod}''  twO 
wing's,  g-reater  and  lesser,  on  either  side,  and  two  projections, 
or  processes,  called  the  pteryg-oid. 

The  body  presents  six  surfaces,  superior,  inferior,  anterior, 
posterior  and  two  lateral. 

The  upper  surface  commences  in  front  in  a  triang-ular 
spine  which,  from  its  articulation,  is  known  as  the  eth- 
moidial  spine  of  the  sphenoid.  Behind  this  projection 
there  may  sometimes  be  seen  a  line  or  ridge  leading-  backward 
and  a  slight  transverse  ridge,  stretching  between  the  anterior 
margins  of  the  optic  foramina.  Behind  this  is  a  broad,  trans- 
verse groove,  the  optic,  and  behind  this  a  prominent,  rounded 
elevation,  the  olivary  ridge  or  process.  Behind  the  olivary 
ridge  is  a  deep  pit-like  depression,  the  sella  turcica  or  pitui- 
tary fossa,  overhanging  which  behind  is  a  square  projection, 
the  dorsum  Ephippii,  whose  posterior  surface,  running  ob- 
liquely downward  and  backward  is  called  the  clivus  Blumen- 
bachii.  On  either  side  of  the  mid-line  in  front  of  the  sella 
turcica  is  a  slight  antero-posterior  groove,  continuous  with  one 
on  the  upper  surface  of  the  Ethmoid,  in  the  articulated  skull, 
for  the  olfactory  bulb.  Behind  the  optic  ridge  the  optic 
«-roove  extends  across  to  terminate  at  either  end  in  the  corres- 
ponding  optic  foramen.  The  olivary  ridge  terminates  at  its 
extremities  in  a  small  projection,  the  middle  clinoid  process, 
which  is  sometimes  connected  by  a  spicule  of  bone  with  the 
anterior  clinoid  process  of  the  lesser  wing.  The  sella  turcica, 
deep  and  pit  like,  is  bounded  in  front  by  the  olivary  ridge,  be- 
hind by  the  dorsum  ephippii,  laterally  by  the  margin  of  the 
carotid  groove.  The  dorsum  sellffi  terminates  at  either  angle 
in  a  rough  projection,  the  posterior  clinoid  process,  sometimes 
connected  to  the  anterior  clinoid  process  by  a  spicule  of  bone. 
The  posterior  surface  of  the  dorsum,  or  the  clivus,  is  a  rough, 
quadrilateral,  sloping  surface,  continuous,  in  the  articulated 
skull  with  the  upper  surface  of  the  basilar  process  of  the 
occipital. 


68  DESCRIPTIVE  ANATOMY. 

The  ^posterior  surface  is  rough  and  square,  presenting- 
many  nipple-like  projections  for  articulation  with  the  basilae 
process  of  the  Occipital.  In  advanced  life  it  is  ossified  to  thr 
Occipital. 

The  anterior  face  -^VQsent^  in  the  middle  a  prominent,  roug-h 
vertical  ridg^e  called  the  crest  of  the  sphenoid,  for  articulation 
with  the  posterior  border  of  the  perpendicular  lamella  of  the 
Ethmoid.  On  either  side  of  the  crest  the  surface  is  roug-h  and 
presents  near  the  middle  the  opening-  into  the  sphenoidal  sin- 
uses. The  marg-ins  of  the  opening-  are  roug-h  for  articulation 
with  the  OS  planum  and  posterior  extremity  of  the  lateral  mass 
of  the  E^thmoid,  the  latter  throug-h  the  pyramid  of  Wistar. 

The  inferior  surface  is  marked  in  the  middle  by  the  contin- 
uation of  the  crest,  called  the  rostrum  of  the  sphenoid.  The 
rostrum  is  broad  behind,  narrow  and  more  prominent  in  front 
and  is  received  into  a  fissure  on  the  upper  border  of  the  '^j 
Vomer.  Oa  either  side  of  the  rostrum  is  a  smooth  surface 
for  articulation  with  theal^  of  the  Vomer,  external  to  which  is 
the  vagfinal  process  for  the  under  surface  of  each  ala,  beneath 
which  is  the  g-roove  called  pteryg-o-palatine,  converted  into  a 
canal  of  the  same  name   bv  articulation   with  the  palate  bone. 

The  lateral  surfaces  are  almost  taken  up  by  the  orig-in  of  the 
g-reater  wings.  The  space  just  above  each  wing-  is  occupied 
by  a  broad  v^nnding-  g-roove,  the  cavernous,  which  terminates 
at  the  lesser  wing-.  In  front  of  this  the  lateral  surfaces 
are  smooth,  slightly  concave  from  above  downward,  and  enter 
into  the  formation  of  the  sphenoidal  fissure  and  the  inner  wall 
of  the  orbit. 

The  Lesser  Wings.  E^ach  lesser  wing  springs  by  its  per- 
forated base  from  the  junction  of  the  lateral  and  superior  sur-  ^ 
faces  of  the  body,  and  passes  outward,  to  terminate  in  a  pointed 
process  near  the  outer  limit  of  the  greater  wing.  They  each 
present  two  surfaces,  superior  and  inferior,  and  two  borders, 
anterior  and  posterior.  The  upper  surface  smooth,  slightly 
concave,  broad  internally  and  narrow  without,  forms  a  part  of 
the  anterior  fossa  of  the  skull.  The  inferior,  narrower  than  the 
superior,  is  smooth  and  slightly  convex  in   outline  and  forms 


OSTEOLOGY.  69 

a  part  of  the  roof  of  the  orbit  and  the  upper  boundary  of  the 
sphenoidal  fissure.  The  anterior  border  is  thin,  straig-ht  and 
serrated  for  articulation  with  the  straig-ht  border  of  the  Front- 
al. The  posterior,  thicker  than  the  anterior,  begins  internally 
in  a  bluntly  pointed  projection  called  the  anterior  clinoid  pro- 
cess, which  passes  backward  and  inward.  This  border  is 
concave  and  smooth,  thinner  in  the  middle  than  at  either  ex- 
tremity, and  terminates  externally  in  the  outer  end  of  the  lesser 
wing".  The  perforation  found  at  the  base  of  the  lesser  wing  is 
the  continuation  of  the  optic  g-roove  of  the  upper  face,  is  called 
the  optic  foramen  and  leads  downward,  forward  and  outward 
to  the  cavity  of  the  orbit. 

The  Greater  Wing-.  The  g"reater  wing*  spring's  from  the 
lower  part  of  the  lateral  aspect  of  the  body  and  passes  upward, 
outward  and  forward.  It  is  divided  into  four  surfaces, 
superior,  anterior,  external  and  inferior.  The  circumfer- 
ence of  the  g-reater  wing-  will  be  described  later.  The  upper 
surface  of  the  g-reater  wing-  is  concave  and  enters  into  the  for- 
mation of  the  middle  fossa  of  the  skull.  It  is,  consequently 
marked  by  elevations  and  depressions  corresponding-  to  the 
sulci  and  convolutions  of  the  temporo-sphenoidal  lobe  of  the 
brain  which  it  lodg-es.  It  is  more  deeply  concave  anteriorly 
where  it  is  overhung  by  the  lesser  wing  than  at  any  other 
part.  Near  the  junction  of  the  wing  with  the  side  of  the  body, 
and  immediately  beneath  the  sphenoidal  fissure,  there  is  a  cir- 
cular foramen  called,  from  its  shape,  the  foramen  rotundum. 
Its  direction  is  downward,  forward  and  slig-htly  outward  and 
its  anterior  opening-  is  found  just  external  to  and  above  the 
base  of  the  pterygoid  process.  Behind  and  external  to  the 
foramen  rotundum  is  the  foramen  ovale,  looking-  directly  down- 
ward and  opening-  on  the  inferior  face  of  the  g-reater  wing-. 
Behind  and  external  to  this  is  found  the  foramen  spinosum, 
also  opening-  directly  downward.  The  external  face  enters 
into  the  formation  of  the  temporal  fossa.  It  is  broader  above 
than  below,  slig-htly  roug-h  for  muscular  attachment,  concave 
both  from  above  downward  and  from  before  backward,  and 
perforated  by  a  number  of  small  foramina.  The  inferior 
face  is  a  part  of  the  y.ygomatic  fossa,  is  small  and  quadrilateral 


70  DESCRIPTIVE  ANATOMY. 

in  shape,  looks  downward  and  outward  and  is  slightly  rough- 
ened for  the  attachment  of  muscles. 

The  g-reater  part  of  the  anterior  face  looks  into  and  forms  a 
part  of,  the  orbital  cavity.  It  is  triang-ular  in  form,  the  apex 
directed  backward  and  inward  and  the  base  outward,  concave 
from  above  downward,  flat  from  before  backward  and  per- 
forated by  one  or  tw^o  small  foramina.  Just  below  this  portion 
of  the  anterior  face  is  a  small  flat  surface  of  bone  formino- 
a  part  of  the  pteryg-o-maxillary  fossa  and  upon  which  the 
foramen  rotundura  opens. 

The  borders.  The  circumference  of  the  greater  wing  may  be 
considered  as  forming  the  borders  of  its  four  surfaces.  From 
the  side  of  the  body  to  the  spine  of  the  sphenoid  is  the  posterior 
border  of  the  upper  surface  ;  from  the  spine  to  the  point  for 
articulation  with  the  parietal  is  the  outer  border  of  the  upper 
surface  ;  from  this  point  to  the  body  again  is  the  upper 
border  of  the  superior  surface.  The  outer  face,  which  is 
quadrilateral  in  form,  has  four  borders.  Its  superior  border 
extends  from  the  outer  border  of  the  upper  face  to  the  ante- 
rior face ;  its  anterior  border  from  this  point  to  the  pterygoid 
ridge  ;  its  inferior  border  is  the  pterygoid  ridge,  while  its 
posterior  border  is  that  part  of  the  outer  border  of  the  upper 
face  extending  from  the  pterygoid  ridge  to  the  summit  of  the 
bone.  The  anterior  face  is  bounded  above,  for  its  outer  part, 
by  a  serrated  edge  forming  the  anterior  boundary  of  the  fron- 
tal triangle  ;  for  its  inner  part  by  a  part  of  the  upper  border 
of  the  superior  surface  ;  anteriorly  or  externally,  by  the  ante- 
rior border  of  the  outer  face  and  below  by  a  ridge  leading  from 
the  pterygoid  ridge  on  the  base  of  the  pterygoid  process.  The 
posterior  border  of  the  upper  surface  is  rough  in  its  outer  half 
for  the  anterior  border  of  the  petrous  portion  of  the  Temporal; 
the  outer  border  is  serrated  for  the  squamous  portion  of  the 
temporal ;  the  outer  part  of  its  upper  border  is  rough  for  the 
Frontal.  The  upper  border  of  the  outer  face  is  articular  for 
the  anterior  inferior  angle  of  the  Parietal;  the  anterior  border  is 
articular  for  the  posterior  border  of  the  orbital  process  of  the 
Malar.  The  inner  part  of  the  upper  border  of  the  superior  face, 
and  the  lower  border  of  the  anterior  face  are  non-articular,  the 


OSTEOLOGY.  71 

one  entering-  into  the  formation  of  the  sphenoidal  fissure  the 
other  into  the  spheno-maxillary.  The  frontal  triang-le  is 
found  at  the  junction  of  the  upper,  outer  and  anterior  surfaces. 
It  is  bounded  in  front  by  the  upper  border  of  the  anterior 
face;  externally  by  the  upper  border  of  the  outer  face;  behind 
b}^  a  part  of  the  upper  border  of  the  superior  surface. 

The  Pterygoid  Process.  The  Pterygoid  Process  springs 
from  the  junction  of  the  greater  wing-  and  the  body  near  the 
posterior  surface  of  the  body.  Each  process  consists  of  two 
plates,  internal  and  external,  united  above  and  diverging  below. 
Viewed  from  the  front  the  united  plates  present  a  triangular 
smooth  surface  above,  forming  the  posterior  wall  for  the  pteryg-o- 
maxillary  fossa,  pierced  above  by  a  round  opening,  the  anterior 
opening  of  the  Vidian  or  pterygoid  foramen.  Below  and 
internal  to  this  is  a  narrow  roug-h  articular  strip  for  the  posteri- 
or border  of  the  vertical  plate  of  the  Palate,  terminating  below 
at  the  divergence  of  the  two  plates.  Posteriorly  the  united 
plates  are  grooved  above  and  bifurcated  below.  Just  above  the 
groove,  more  on  the  posterior  border  of  the  greater  wing  than 
on  the  pterygoid  process,  is  the  posterior  opening  of  the  Vidian 
canal.  Below  this  the  posterior  border  of  the  inner  plate  shows 
an  oblong,  shallow  fossa,  the  scaphoid,  while  internal  to  this 
is  the  opening-  of  a  small  foramen,  the  pteryg^o-palatine.  Below 
and  external  to  the  scaphoid  fossa  is  the  pterygoid  fossa,  formed 
by  the  junction  of  the  two  plates  in  the  separated  bone  but  filled 
in  below  in  the  skull  by  the  tuberosity  of  the  palate.  The 
pteryg-oid  fossa  is  deeper  and  broader  at  its  upper  portion. 
The  inner  plate  is  longer  and  narrower  than  the  outer.  Its 
internal  surface  is  smooth  and  forms  the  outer  boundary  of  the 
posterior  nares,  its  outer,  smooth  and  concave,  forms  the  inner 
boundary  of  the  pterygoid  fossa.  The  anterior  border,  blended 
with  the  outer  plate,  above,  presents  below  a  serrated  margin 
for  a  groove  on  the  palate.  Its  posterior  border  is  thin  and 
sharp  and  terminates  below  in  a  thin  curved  plate  of  bone,  the 
hamular  process,  which  projects  below  the  level  of  the  outer 
plate,  and  is  curved  outward  and  backward.  The  outer  plate, 
broader  and  more   massive  than  the  inner,   presents  an  outer 


72  DESCRIPTIVE  ANATOMY. 

face  which  is  concave  and  roug-h  to  form  the  inner  wall  of  the 
zyg-omatic  fossa,  an  internal  face,  roug-h  and  irregularly  con- 
cave, which  forms  the  outer  wall  of  the  pteryg-oid  fossa;  an 
anterior  border  serrated  below  for  the  gfroove  on  the  Palate, 
and  a  posterior  border  which  is  thin,  sharp  and  irregular, 
sloping-  obliquely  downward  and  backward. 

The  Ethmoid. 

The  Ethmoid  lies  in  the  middle  of  the  anterior  fossa  of  the 
skull.  It  consists  of  a  body  and  two  lateral  masses.  A  por- 
tion of  the  body  can  be  seen  by  looking-  into  the  anterior  fossa 
of  the  skull,  and  part  of  the  lateral  masses  by  looking*  into 
the  orbital  cavity;  but  the  larg-er  portion  of  the  bone  is  con- 
cealed by  surrounding-  bones. 

The  Siiferior  Surface  of  the  body  is  called  the  Horizontal 
or  Cribriform  Plate;  and  is  perforated  by  numerous  small 
foramina.  These  foramina  are  arranged  in  three  rows,  of 
which  the  internal  and  external  are  fairly  distinct,  while  the 
middle  row  is  irreg-ular  and  indistinct.  The  anterior  foramen 
of  the  internal  row  is  a  narrow,  slit-like  aperture  for  the 
transmission  of  a  nerve.  The  cribriform  plate  is  a  depressed 
surface,  concave  from  side  to  side  and  marked  on  the  mid-line 
by  a  projection,  called  the  crista  g-alli  (Iv.  A  cock's  comb). 
This  projection  commences  near  the  posterior  end  of  the  bone; 
and  rapidly  rising-  in  height,  terminates  near  the  anterior 
end  of  the  bone  in  a  blunt,  rounded  point.  Its  posterior  bor- 
der is  narrow  and  sharp.  Its  lateral  apects,  smooth  and 
slightly  concave  at  the  lower  portion,  are  marked  above  by  a 
bulging-  projection,  which  varies  g-reatly  in  size  in  different 
bones.  Projecting-  from  the  front  of  the  crista  g-alli  are  two 
small  processes,  one  towards  either  side,  called  the  alar 
■processes  (Iv.  Ala,  a  wing-). 

At  each  side  of  the  base  of  the  crista  Galli  is  a  small  fissure 
called  the  nasal  g-roove,  or  slit.  Posteriorly  the  superior  sur- 
face presents  a  deep  notch,  the  sphenoidal  fissure,  for  the 
reception  of  the  ethmoidal  spine  of  the  sphenoid  bone. 

Laterally  this  surface  articulates  with  the  orbital  plate  of 
the  frontal  bone;  anteriorly  with  the  frontal  bone  by  the  two 


OSTEOLOGY.  73 

alar  processes  which  complete,  posteriorly,  an  opening"  called 
the  foramen  coecum. 

From  the  lower  surface  of  the  cribriform  plate  there  passes 
downward,  on  the  middle  line,  a  thin  sheet  of  bone  called  the 
perpendicular  lamella,  which  aids  in  forming-  the  septum  of 
the  nose,  articulating-  in  front  with  the  nasal  spine  of  the 
frontal  and  with  the  nasal  bones;  posteriorly  it  articulates 
above  with  the  beak  of  the  sphenoid,  below  with  the  vomer; 
inferiorly  it  g-ives  attachment  to  the  cartilage  of  the  septum. 
Its  faces  are  g-rooved. 

The  lateral  mass  lies  to  the  side  of  the  perpendicular  lamella, 
with  a  slight  interval  between;  it  presents  an  outer,  inner  and 
superior  face.  The  outer  surface  forms  part  of  the  inner  wall 
of  the  orbit;  it  is  smooth,  flat  and  quadrilateral  and  is  called 
the  OS  planum;  its  upper  part  is  marked  by  two  g-rooves,  which 
are  the  anterior  and  posterior  ethmoidal  foramina.  The  inter- 
nal surface  is  convex,  roug-h  and  fissured  behind;  this  fissure 
is  called  the  superior  meatus  of  the  nose;  above  this  is  a  curved 
portion  of  the  bone  called  the  superior  turbinated  bone;  below 
the  superior  meatus  is  another  portion  called  the  middle  tur- 
binated bone,  which  is  the  upper  limit  of  the  middle  meatus 
of  the  nose.  The  superior  surface  of  the  lateral  mass  pre- 
sents numerous  irreg-ular  opening's  into  the  cells,  of  which  this 
part  of  the  bone  is  made  up;  these  are  closed  in  by  the  over- 
lapping- horizontal  plate.  Projecting- downward  and  backward 
from  the  lower  edg-e  of  the  lateral  mass  is  a  thin  plate  of  bone 
called  the  unciform  process,  which  articulates  with  the  ethmoi- 
dal process  of  the  inferior  turbinated  and  helps  to  close  the 
opening-  of  the  antrum  maxillare.  From  the  posterior  extrem- 
ity of  the  lateral  mass  there  projects  backward  a  triangfular, 
curled,  pointed  process,  which  extends  into  the  sphenoidal  cell 
of  that  side,  and,  as  puberty  approaches,  becomes  detached 
from  the  ethmoid  and  ossified  to  the  sphenoid;  it  is  called  the 
sphenoidal  spong-y  bone,  or  pj^ramid  of  Wistar.  The  cells,  of 
which  the  lateral  mass  consists,  are  separated  by  a  transverse 
septum  into  the  two  sets,  the  anterior  and  posterior  ethmoidal 
cells;  the  anterior  communicate  with   the  middle  meatus  by  a 


74  DESCRIPTIVE  ANATONY. 

tortuous  canal  called  the  infundibulum,  with  which  the  frontal 
sinusalso  communicates.  The  infundibulum  opens  into  the  up- 
per front  part  of  the  middle  meatus  by  a  larg"e  orifice.  At  the 
upper  back  part  of  the  superior  meatus  is  an  orifice  which 
leads  into  the  posterior  ethmoidal  cells. 

The  Nasal  Bones. 

The  Nasal  Bones  are  two  somewhat  flat  bones,  forming-  the 
bridge  of  the  nose,  along-  the  centre  of  which  they  articulate 
with  each  other.  They  are  somewhat  quadrilateral ;  and  pre- 
sent for  examination  two  surfaces,  anterior  and  posterior,  two 
borders,  internal  and  external,  and  two  extremities,  superior 
and  inferior.  The  anterior  face  which  looks  forward  and 
slig-htly  outward  is  concave  from  above  downward  ;  and 
slig-htly  convex  from  side  to  side,  the  anterior  surface  being-  a 
little  roug-hened  and  marked  by  nutrient  foramina.  The 
^posterior  surface,  which  looks  inward  as  well  as  backward, 
is  convex  from  above  downward  ;  and  marked  near  the  inter- 
nal border  by  a  vertical  g-roove.  The  superior  extremity  is 
thicker  and  more  massive  than  the  inferior  ;  and  is  roug-hened 
and  serrated  for  articulation  with  the  nasal  notch  of  the  fron- 
tal bone.  The  inferior  extremity  is  broader  and  thinner  than 
the  superior  ;  and  slopes  obliquely  from  within  outward  and 
downward,  so  that  v^^hen  the  two  bones  are  articulated,  a  pear- 
shaped  notch  is  found  between  them,  its  apex  upward  and  its. 
base  downward.  The  internal  border  is  shorter  than  the  ex- 
ternal ;  and  presents  when  articulated  with  its  fellow  a  well- 
defined  crest  for  articulation  with  the  nasal  spine  of  the  fron- 
tal and  the  perpendicular  lamella  of  the  ethmoid  bone.  The 
external  border,  long-er  than  the  internal,  is  serrated,  thin,  and 
sharp  for  articulation  with  the  nasal  process  of  the  superior 
maxillary. 

Lachrymal  Bone. 

The  lachrymal  bones  are  a  pair  of  small  bones,  one  being- 
found  on  the  inner  wall  of  each  orbit  in  front  of  the  os  planum. 
The  bone  remotely  resembles  a  fing-er  nail  and  hence  acquires 
its  synonjmi  of  ung-uis.  It  presents  two  faces,  two  extremities 
and  two  borders.     The  external  face  is  divided  into  an  anterior 


OSTEOLOGY.  75 

and  a  posterior  portion,  by  a  vertical  ridge,  which  terminates 
inferiorly  in  a  hook-like  process  called  hamular.  The  poste- 
rior and  larg-er  portion  is  part  of  the  inner  wall  of  the  orbit  and 
is  flat  and  smooth.  The  anterior  portion  is  a  vertical  groove, 
called  the  lachrymal. 

The  internal  face  is  rough  for  articulation  with  the  ethmoid 
bone,  and  presents  a  vertical  groove  corresponding  to  the  verti' 
cal  ridge  on  the  opposite  side  ;  the  portion  of  the  surface  in 
front  of  this  groove  enters  into  the  formation  of  the  middle 
meatus. 

The  upper  extremity  articulates  with  the  internal  angular 
process  of  the  frontal  bone. 

The  lower  extremity  is  divided  into  two  parts,  the  posterior 
articulating  with  the  orbital  plate  of  the  superior  maxillary, 
the  anterior  projecting  farther  downward  and  articulating 
with  the  lachrymal  process  of  the  inferior  turbinated. 

The  anterior  border  articulates  with  the  nasal  process  of 
the  superior  maxillary  bone. 

The  posterior  border  articulates  with  the  os  planum. 

Inferior  Turbinated  Bone. 

The  inferior  turbinated,  or  inferior  spongy  bone,  is  found 
on  the  lower  part  of  the  outer  wall  of  the  nasal  fossa;  the 
middle  and  superior  turbinated  bones  are  merely  parts  of  the 
ethmoid.  The  bone  is  divisible  into  two  extremities,  two 
faces  and  two  borders. 

The  anterior  extremity  is  much  the  larger  and  articulates 
with  the  inferior  turbinated  crest  of  the  superior  maxillary. 

The  posterior  extremity  is  slender  and  pointed  aud  articu- 
lates with  the  inferior  turbinated  crest  of  the  palate  bone. 

The  internal  face  is  convex  and  marked  by  apertures  and 
grooves. 

The  external  face  is  concave  and  enters  into  the  inferior 
meatus  of  the  nose. 

The  inferior  border  is  rounded  and  free,  marking  the  limit 
between  the  middle  and  inferior  meatus. 

The  superior  border  articulates  from  before  backward  with 
the  sujjerior  maxillary,  the   lachrymal,   the  ethmoid  and  the 


76  DESCRIPTIVE  ANATOMY. 

palate  bones.  It  presents  three  processes,  lachrymal,  ethmoid 
and  maxillary.  The  lachrymal  process  is  directed  upward  to 
articulate  with  the  lower  extremity  of  the  lachrymal  bone, 
and  with  the  nasal  process  of  the  superior  maxillary,  aiding-  to 
form  the  lachrymal  canal. 

The  maxillary  process  is  larger  than  the  other  two  and  is  a 
curved  plate  of  bone  directed  downward  and  outward  from 
the  base  of  the  ethmoidal  process  and  articulates  with  the 
superior  maxilary  by  hooking-  around  the  orifice  of  the  antrum. 
The  ethmoidal  process  is  behind  the  lachrymal,  and  is  directed 
upward  to  articulate  with  the  unciform  process  of  the  ethmoid. 

Vomer. 

The  vomer  is  a  single  bone  found  separating  the  nostrils 
behind  and  below,  forming  part  of  the  septum  of  the  nose; 
the  upper  part  of  the  septum  is  the  perpendicular  lamella  of 
the  ethmoid;  the  anterior  part  is  a  plate  of  cartilage.  It  pre- 
sents two  faces  and  four  borders. 

The  faces  are  lateral  and  each  forms  part  of  the  inner  wall 
of  a  nostril,  the  bone  usually  bulging  toward  one  or  the  other. 
They  are' marked  by  shallow  furrows  and  by  the  naso-pala- 
tine  groove,  which  is  directed  obliquely  downward  and  for- 
ward on  each  face. 

The  superior  border  presents  an  antero-posterior  groove 
which  receives  the  rostrum  of  the  sphenoid  ;  the  edges  of 
the  groove  are  projected  outward  into  lips,  or  alae,  each  of 
which  lies  in  the  groove  above  the  vaginal  process  of  the 
sphenoid. 

The  inferior  border  is  received  between  the  averted  edges 
of  the  palate  processes  of  the  superior  maxillary  bones  and  of 
the  horizontal  plates  of  the  palate  bones. 

The  anterior  border  presents  a  long-itudinal  fissure  which 
receives  superiorly  the  perpendicular  lamella  of  the  ethmoid, 
inferiorly  the  triangular  cartilage  of  the  septum;  the  lower 
part  is  occasionally  not  fissured  but  rough. 

The  posterior  border  is  concave  and  free,  terminating, 
posteriorly,  the  septum  of  the  nose. 


OSTEOLOGY.  77 


Malar  Bone. 

The  malar  bone  forms  the  prominence  of  the  cheek,  is 
somewhat  quadrang-ular  and  presents  for  examination  four 
processes  and  a  body  with  two  surfaces  and  four  borders. 

The  anterior,  or  external  face  is  convex  and  has  several  fora- 
mina opening"  on  it,  called  malar. 

The  posterior,  or  internal  face  is  smooth  and  concave, 
entering-  into  the  temporal  fossa  above  and  the  2jyg-omatic  be- 
low. 

T\iQ  frontal  f>rocess  projects  upward  to  articulate  with  the 
external  ang-ular  process  of  the  frontal  bone.  The  orbital 
firocess  is  a  smooth  projecting-  lip  of  bone  curving-  downward 
from  the  frontal  process,  and  projecting-  inward,  forming-  a 
concavity  which  enters  into  the  outer  wall  and  floor  of  the 
orbit.  Its  lower  surface  forms  part  of  the  temporal  fossa. 
Superiorly  it  articulates  with  the  frontal  bone.  Posteriorly 
it  articulates  with  the  sphenoid  bone  ;  internal  to  which  it  ar- 
ticulates with  the  orbital  plate  of  the  superior  maxillary  bone  ; 
between  these  two  articulations  there  is  often  seen  the  narrow, 
rounded,  non-articular  anterior  extremity  of  the  spheno-max- 
illary  fissure.  This  process  presents  the  opening-s  into  one  or 
more  small  canals,  temporo-malar,  which  extend  to  the  anterior 
surface  of  the  bone  and  some  usually  to  the  posterior  surface. 

The  maxillary  froccss  is  roug-h  and  triang-ular,  articulating* 
with  the  superior  maxilla. 

The  2yg-o?jiatic  process  extends  backwards,  is  long-  and  nar- 
row and  articulates  with  the  zyg-omatic  process  of  the  temporal. 

The  superior  border  is  concave,  smooth  and  rounded,  and 
forms  part  of  the  marg-in  of  the  orbit. 

The  injcrior  border  is  straig-ht  and  continuous  with  the 
lower  edg-e  of  the  zyg-oma. 

The  anterior  border  is  straig-ht  and  roug-h  to  articulate  with 
the  superior  maxilla. 

The  posterior  border  is  sinuous  and  continuous  with  the 
temporal  ridg-e  above,  and  below  with  the  upper  edg-e  of  the 
zygoma. 


78  DESCRIPTIVE  ANATOMY. 

Superior  Maxillary. 

The  superior  maxillary  bones  form  the  upper  jaw  and  are, 
with  the  exception  of  the  inferior  maxillary,  the  largest  bones 
of  the  face.  E)ach  bone  m-ticulates  with  the  frontal  and 
etliinoid.,  and  all  the  hones  of  the  face  except  the  inferior 
maxillary .    The  bone  is  divisible  into  a  bodya.r\.^  four  f>rocesses. 

The  body  is  irregfularly  quadrilateral,  is  hollowed  out  into  a 
cavity  called  the  antrum  of  Hig*hmore,  or  antrum  maxillare, 
and  presents  four  faces — anterior^  superior,  -posterior  ^  inte^-nal. 

The  anterior  or  facial  surface  is  somewhat  concave  and 
presents  about  its  centre  a  depression,  called  the  canine  fossa, 
which  is  limited  internally  by  a  vertical  ridg^e,  the  canine 
ridg-e;  on  the  inner  side  of  the  canine  ridg^e  is  another  depression, 
the  incisive  fossa;  just  above  the  canine  fossa  is  a  foramen,  the 
infra-orbital.  This  surface  is  limited  internally  by  the  thin 
concave  edg-e  of  the  nasal  fossa:  below  by  the  alveolar  process; 
externally  by  the  malar  process  and  a  ridg-e  descending-  from 
it ;  superiorly  by  the  margfin  of  the  orbit. 

The  posterior  or  zyg-omatic  surface  is  chiefly  occupied  by  a 
roug-h  bulg"e,  the  tuberosity  of  the  superior  maxillary  bone;  it 
presents  numerous  small  foramina,  and  at  its  lower  part  a 
toug-h  oval  surface;  above  and  internal  to  this  is  a  smooth  spiral 
g-roove,  which,  with  a  similar  g-roove  on  the  palate  bone,  forms 
the  posterior  palatine  canal.  The  upper  limit  of  this  surface, 
separating"  it  from  the  orbital  face,  is  a  smooth  rounded  border, 
on  which  is  a  notch,  the  commencement  of  the  infra  orbital 
canal.  The  malar  process  separates  this  face  from  the  anterior; 
below  it  is  limited  by  the  alveolar  process. 

The  superior  or  orbital  surface  forms  the  floor  of  the  orbit. 
It  is  formed  of  a  thin  triang-ular  plate  of  bone,  is  smooth, 
sloping-  downward  and  forward,  and  marked  from  behind  for- 
ward, by  a  g-roove,  the  infra-orbital  canal,  which  disappears  in 
the  bone  to  terminate  at  the  infra-orbital  foramen  on  the 
anterior  face.  This  face  is  bounded  internally  by  a  roug-h  edge 
for  articulation  from  behind foriuard,  with  th.Qpalate,  ethmoid 
and  lachrymal  bones;  anteriorly  it  is  limited   by  the  lower 


OSTEOLOGY.  79 

marg-in  of  the  orbit,  internally,  and  externally,  by  a  roug"h 
border  for  articulation  with  the  malar  bone;  externally  it  is 
separated  from  the  posterior  surface  by  a  rounded  border  on 
which  beg"ins  the  infra-orbital  canal  by  a  notch  ;  this  border 
forming-,  in  the  articulated  skull,  the  lower  marg-in  of  a  fis- 
sure, the  spheno-maxillary. 

The  internal  or  nasal  surface  aids  in  forming-  the  outer  wall 
•of  the  nose,  and  presents  a  larg-e  irreg-ular  aperture  leading- 
into  the  antrum  of  Hig-hmore  ;  this  aperture  is  much  reduced 
by  articulations  with  neig-hboring-  bones,,  J)alale,  ethmoid,  lach- 
rymal and  inferior  turbinated.  The  antrum  is  indistinctlj'- 
triangular  ;  in  it  are  seen  numerous  vertical  g-rooves  and  on 
its  floor  several  conical  projections  which  mark  the  position 
of  molar  teeth.  In  front  of  the  opening-  into  the  antrum  is  a 
deep  vertical  g-roove,  the  sulcus  lachrymalis.  This  face  is 
limited  above  by  the  nasal  process,  in  front,  and  behind  this 
by  a  roug-h  cellular  edg-e  for  articulation  with  the  lachrymal 
and  ethmoid  bones;  interiorly  is  the  horizontal  palate  process, 
which  may  be  said  to  divide  it  into  two  portions,  the  part  be- 
low terminating-  in  the  alveolar  process  and  the  part  above 
forming-  the  inferior  meatus  of  the  nose.  The  posterior  bor- 
ber  is  roug-h  for  articulation  with  the  palate  bone.  The  ante- 
rior edg-e  is  sharp  and  concave  and  forms  the  marg-in  of  the 
anterior  nares. 

The  four  processes  are  nasal,  malar,  -palate  and  alveolar. 
The  nasal  process  is  a  long-,  thin,  triang-ular  projection  form- 
ing- a  part  of  the  wall  of  the  nose  and  presenting-  three  borders 
and  tzijo  surfaces. 

The  anterior  border  is  convex,  thin  and  serrated  for  articu- 
lation with  the  nasal  bone. 

The  posterior  border  is  thick  and  g-rooved,  the  posterior 
marg-in  of  the  process  is  roug-h  for  articulation  with  the  lacry- 
mal  bone  ;  the  anterior  marg-in  is  rounded,  continued  into  the 
marg-in  of  the  orbit,  and  presents  below  a  small  tubercle. 
This  g-roove,  in  the  articulated  skull,  is  formed  into  a  canal  for 
lodg-ing-  the  nasal  duct,  and  is  nearly  vertical,  being-  slig-htly 
oblique  backward  and  outward.     The  upper  border  is  blunt 


80  DESCRIPTIVE  ANATOMY. 

and  serrated  for  articulation  with  the  frontal  bone,  its  internal 
ang"ular  process. 

The  external  face  is  concave  and  marked  by  small  foramina. 

The  internal  face  is  crossed  from  behind  forward  by  two 
roug-h  ridg-es,  crista  turbinalis  inferior  and  superior,  the 
former  articulating-  with  the  inferior  turbinated  and  the  latter 
with  the  ethmoid.  Above  the  superior  turbinated  crest  the 
surface  is  rough  for  articulation  with  the  ethmoid  ;  between 
the  two  crests  it  is  smooth  and  concave,  entering-  into  the  mid- 
dle meatus  of  the  nose. 

The  malar  -process  forms  the  upper  part  of  the  boundary'- 
between  the  anterior  and  posterior  faces.  It  is  concave  both 
in  front  and  behind,  triang-ular  in  outline  and  its  summit  is 
rough  for  articulation  with  the  malar  bone. 

Tht  palate  process  projects  inward  from  the  lower  part  of 
the  internal  surface,  forming-  a  portion  of  the  floor  of  the  nose 
and  the  roof  of  the  mouth.  It  does  not  extend  as  far  back  as 
the  body  of  the  bone,  but  may  be  said  to  be  deficient  behind. 
Its  upper  surface  is  transversel}'-  concave  and  smooth.  In 
front  is  a  foramen  which  leads  into  the  anterior  palatine  canal, 
which  appears  on  the  inner  border  of  the  process  as  a  g-roove. 
Its  lower  surface  is  also  concave,  but  /roug-h,  marked  by  nu- 
merous shallow  depressions  and  by  a  g-roove  externally,  which 
runs  from  behind  forward.  The  inner  border  is  roug-h  to  ar- 
ticulate with  its  fellow  on  the  opposite  side  ;  it  is  thicker  ante- 
riorly than  posteriorly,  and  its  upper  edg-e  is  raised  into  a 
ridg-e,  or  crest,  which  is  slig-htly  averted,  so  as  to  produce, 
when  the  bone  is  articulated,  a  narrow  g-roove,  for  the  recep- 
tion of  the  vomer.  Towards  the  front  the  inner  border,  in 
its  lower  part,  presents  a  g-roove,  which  sinks  into  the  bone 
above  to  communicate  with  a  foramen  on  the  upper  surface, 
the  anterior  palatine.  In  front  the  inner  border  terminates  in 
a  slender,  pointed  process,  which,  united  with  a  similar  ©ne 
on  the  opposite  bone,  forms  the  anterior  nasal  spine. 

The  anterior  border  of  the  process  is  the  thin  concave  mar- 
g-in  of  the  nose,  the  nasal  notch. 

T\i&  posterior  border  is  straight  and  serrated  for  articulation 
with  the  horizontal  plate  of  the  palate  bone. 


OSTEOLOGY.  81 

The  areolar  process  projects  downwards  from  the  lower, 
outer  part  of  the  bone,  and  forms  about  a  fourth  of  the  circum- 
ference of  a  circle.  It  is  marked  by  sockets  for  eight  teeth, 
with  interv^ening-  septa. 

Palate  Bone. 

The  palate  bone  enters  into  the  formation  of  the  orbits,  the 
nasal  fossa?  and  the  roof  of  the  mouth.  It  is  divided  into  hori- 
zoiital  and  vertical,  or  perpoidicular  portions,  or  plates. 

The  horizontal  -portion  projects  inward,  at  about  a  right 
angle,  from  the  lower  limit  of  the  vertical  plate,  and  presents 
two  surfaces  and  three  borders.  The  superior  or  nasal  face 
is  smooth  and  concave  transversely,  forming  the  back  part  of 
the  floor  of  the  nose.  The  inferior  face  is  also  slightly  con- 
cave transversely  and  rough,  forming  the  posterior  part  of  the 
hard  palate.  A  transverse  ridge  crosses  it  posteriorly.  The 
anterior  border  is  serrated  for  articulation  with  the  palate 
process  of  the  superior  maxillary. 

The  posterior  Ijorder  is  smooth,  concave  and  free,  having  its 
inner  extremity  prolonged  backwards  by  a  slender,  sharp  pro- 
cess, which  with  asimilar  projection  on  the  opposite  bone,  forms 
the  posterior  nasal,  or  palate  spine.  The  internal  border  is 
thick,  rough  and  serrated  for  articulation  with  its  fellow;  the 
upper  edge  of  this  border  is  raised  and  produces,  when  articu- 
lated, a  slight  groove  for  the  reception  of  the  vomer. 

The  vertical  plate  is  irregularly  quadrangular  and  presents 
two  faces,  internal  and  external,  and  three  borders,  superior, 
anterior  and  posterior.  The  internal  surface  presents  two 
transverse  ridges,  the  superior  and  inferior  turbinated  crests; 
the  inferior  to  articulate  with  the  inferior  turbinated  bone, 
and  the  superior  with  the  middle  turbinated  bone  of  the  eth- 
moid. This  surface,  below  the  inferior  turbinated  crest,  is 
concave  and  forms  the  outer  boundary  of  the  inferior  meatus 
of  the  nose;  the  surface  between  the  two  crests  is  also  concave, 
and  forms  a  part  of  the  middle  meatus;  above  the  superior 
crest  is  a  narrow  groove. 

The  exteriml  surface  is,  to  a  great  extent,  rough  for  articu- 
lation with  the  internal  face  of  the  superior  maxilla  ;  but  at 
Des  Anat — 6 


82  DESCRIPTIVE  ANATONY. 

its  Upper  back  part  there  is  a  smooth  portion,  which  forms  a 
part  of  the  spheno-maxillary  fossa.  At  the  posterior  part  of 
this  face  is  a  vertical  g-roove,  converted  into  the  posterior  pala- 
tine canal  by  articulation  with  the  tuberosity  of  the  superior 
maxilla. 

The  superior  border  presents  two  processes,  separated  by 
a  deep  notch.  The  notch  is  called  spheno-palatine,  and  is  con- 
verted into  a  foramen  of  that  name  by  the  articulation  of  the 
sphenoid  bone.  The  anterior  process  is  known  as  the  orbital; 
the  posterior  as  the  sphenoidal.  The  orbital  process  inclines 
outward  as  it  ascends,  is  hollow  and  hig^her  than  the  sphen- 
oidal, being-  perched  upon  a  thin  plate  of  bone,  its  neck.  It 
presents  five  faces^anterior,  posterior,  internal,  external  and 
superior — the  first  three  being-  articular,  the  others  non- 
articular. 

The  anterior  face  articulates  with  the  orbital  surface  of  the 
superior  maxillary. 

^h.^  posterior  face  articulates  with  the  sphenoid  bone. 

The  internal  face  articulates  with  the  ethmoid  bone  and 
usually  presents  the  opening-  into  the  cellular  cavity  in  the 
process;  but  this  is  sometimes  on  the  posterior  face. 

The  external  face  forms  a  part  of  the  inner  wall  of  the 
spheno-maxillary  fossa. 

The  superior  face  forms  the  back  part  of  the  floor  of 
the  orbit. 

The  sphenoidal  process  is  a  thin  plate  of  bone,  inclining-  in- 
ward as  it  ascends,  and  presents  three  faces^ — superior,  ex- 
ternal and  internal — and  two  borders — anterior  and  posterior. 

The  superior  face  articulates  with  the  sphenoid  bone  and 
presents  a  g-roove,  converted,  by  articulation,  into  the  pterygo- 
palatine canal. 

The  external  face  partly  enters  into  the  formation  of  the 
spheno-maxillary  fossa,  and  partly  articulates  with  the  ptery- 
goid process  of  the  sphenoid. 

The  internal  face  is  free  and  forms  part  of  the  outer  wall  of 
the  nasal  fossa. 


OSTEOLOGY.  83 

The  anterior  border  of  the  process  is  the  posterior  boundary 
of  the  spheuo-palatine  notch. 

The  -posterior  border  of  the  process  articulates  with  the 
pter3^g-oid  process  of  the  sphenoid  bone. 

The  anterior  border  of  the  perpendicular  plate  is  irreofular, 
articulates  with  the  superior  maxillary  bone  and  presents,  at  the 
intersection  of  the  inferior  turbinated  crest,  a  thin  process,  the 
maxillary,  which  aids  in  closing*  the  openino-  into  the  antrum 
maxillare. 

The  -posterior  border  of  the  perpendicular  plate  is  g-rooved 
and  articulates  with  the  pteryg-oid  process  of  the  sphenoid. 
At  its  lower  part  is  a  process,  the  pteryg-oid  process,  or  tuber- 
osity of  the  palate  bone.  It  is  triang-ular,  is  directed  down- 
ward and  backward  and  outward,  and  fits  into  the  interval 
between  the  two  plates  of  the  pteryg-oid  process  of  the  sphenoid. 
Descending-themiddleof  the  tuberosity,  posteriorly,  isa  smooth 
gToove,  which,  when  the  bone  is  articulated,  forms  part  of  the 
pteryg-oid  fossa;  on  each  side  of  this  g-roove  is  a  roug-h  g-roove, 
which  articulates  with  the  corresponding- plate  of  the  pteryg-oid 
process  of  the  sphenoid.  Kxternally  the  tuberosity  is  roug-h 
and  articulates  with  the  superior  maxilla.  The  opening-s  of 
numerous  canals,  the  accessory  posterior  palatine  canals,  are 
seen  on  the  tuberosity,  and  it  is  perforated  vertically  throug-h 
its  base  by  the  posterior  palatine  canal. 

The  Inferior  Maxilla. 

The  inferior  maxilla,  or  lower  jaw  bone,  is  a  symmetrical 
bone,  derived  from  lateral  halves,  which  blend  in  the  middle 
line — each  lateral  half  consisting-  of  a  vertical  portion,  the 
ramus,  and  a  horizontal  portion,  which  is  one  half  of  the  body 
of  the  bone. 

The  j9o</y  is  of  a  horse-shoe  shape;  and  presents  external 
and  internal  surfaces,  superior  and  inferior  border's.  The 
surfaces  do  not  look  directly  outward  and  inward  ;  but  the 
external  inclines  outward  and  forward,  and  the  internal  inward 
and  backward.  The  external  surface  is  convex  from  side  to 
side,  concave  in  some  ]K)rtions,  from  above  downward. 

In  front,   on  the  mid-line  of  the  body,   is  a   vertical  ridg-e, 


84  DESCRIPTIVE  ANATOMY. 

the  Symphysis  Menti  (Iv.  Mentiim,  the  chin),  or  Crista  Men- 
talis,  which  as  it  descends  spreads  out  so  as  to  form  a  triangu- 
lar projection,  the  meiital -process,  which  forms  the  prominence 
of  the  chin.  E^xternal  to  this  symphysis  is  a  depression, 
called  the  Incisive  Fossa  ;  and  just  beyond  this  is  a  larg-e 
and  well-marked  foramen,  the  Mental  Forameji.  E^xtending- 
backward  and  upward  from  the  mental  foramen  is  a  promi- 
nent ridge  of  the  bone,  which  becomes  continuous  with  the 
anterior  border  of  the  ramus,  called  the  External  Oblique 
Ridge. 

The  Internal  surface  is  concave  from  before  backward, 
irregular  in  outline  from  above  downward.  On  the  mid-line 
of  the  internal  surface  is  a  vertical  groove  corresponding  to  the 
symphysis,  on  either  side  of  this  groove  are  seen  two  tuber- 
cles, one  inferior  and  one  superior,  both  a  little  below  the 
middle  point  of  the  groove  ;  which  are  known  as  the  Genial 
Tubercles ,  superior  and  inferior,  sometimes  called  the  Spines 
Men  tales. 

They  are  very  irregular  in  formation  :  sometimes  all  four  of 
them  coalesce  into  a  singde  roughened  process  ;  sometimes 
there  are  two  flat  ones  on  either  side  of  the  mid-line  ;  and 
occasionally  the  four  are  distinctly  seen.  External  to  the 
genial  tubercles  is  a  slight  depression,  which  in  the  fresh 
state  lodges  the  sub-lingual  gland.  E^xternal  to  and  below 
the  tubercles,  is  a  slighter  depression,  called  the  Diga.stric 
Fossa,  serving  for  the  attachment  of  the  muscle  of  that  name. 
Extending  upward  and  backward  from  the  digastric  fossa, 
and  lying  nearly  opposite  to  the  external  oblique  ridge,  is 
a  prominent  ridge  of  bone,  called  the  Internal  Oblique  Ridge, 
or  Mylo-Hyoidean  Ridge.  Below  this  ridge  and  parallel  to 
it  is  a  long  groove,  which  is  called  the  Submaxillary  Fossa. 
The  upper  border  of  the  bone  is  called  the  Alveolar  Process 
(L.  Dim.  of  Alveus,  a  cavity)  ;  and  presents  the  depressions 
for  sixteen  teeth,  these  sockets  being  separated  from  one 
another  by  intervening  bony  septa.  The  lozuer,  or  basilar, 
border  is  slightly  everted,  strong  rounded  and  smooth.  It  is 
the  most  prominent  portion  of  the  bone  in  the  living  man.    Usu- 


OSTEOLOGY.  85 

ally  about  an  inch  in  front  of  the  ang-le  of  the  jaw  this  border 
presents  a  slig-ht  g-roove,  across  which  passes  the  facial  artery. 
The  Ramus  is  a  quadrilateral  projection  of  bone,  which  ex- 
tends nearly  vertically  upward,  almost  at  rig-ht  angles  with 
the  body  of  the  bone.  Its  obliquit}^  varies  with  the  different 
periods  of  life.  The  ramus  is  divided  for  study  into  two  sur- 
faces, external  and  internal,  and  four  borders,  anterior,  pos- 
terior, superior  and  inferior.  The  external  surface  is  flat,  is 
slightly  roug-hened  for  muscular  attachment;  and  presents  no 
other  mark  of  interest.  The  internal  face,  slightly  concave 
from  before  backward,  is  marked  about  its  centre  by  a  very 
prominent  projecting  lip  of  bone,  above  which  is  seen  the 
opening  of  a  canal.  Above  this  opening  there  is  a  slight 
groove.  The  foramen  leads  into  a  canal  which  extends 
through  the  bone,  the  Dental  Canal,  and  the  canal  termi- 
nates at  the  mental  foramen  on  the  external  surface  of  the 
body.  It  is  so  located  as  to  pass  in  close  contact  with  the  roots 
of  the  teeth,  and  lodge  the  blood-vessels  and  nerves  which 
supply  the  fangs  of  each  one  of  the  teeth  of  the  lower  jaw. 
The  projection  of  bone  which  guards  the  foramen  below 
and  in  front  is  called  the  Lingula.  The  anterior  border  is 
thicker  than  the  posterior;  and  is  marked  by  a  nearly  vertical 
groove,  which  is  surmounted  by  two  lips.  Of  these  the  external 
lip,  more  prominent  and  sharper  than  the  internal,  is  the  up- 
ward continuation  of  the  external  oblique  ridge;  while  the  inner 
lip  is  an  abutment  that  rises  from  the  termination  of  the 
alveolar  process,  and  becomes  nearly  continuous  with  the 
mylo-hyoid  ridge  on  the  inner  face  of  the  body.  The 
posterior  border  is  more  rounded  and  thinner  than  the  ante- 
rior, extending  above  into  one  of  the  projections  of  the  upper 
border,  and  below  terminating  at  the  angle  of  the  jaw.  The 
hnjer  border  of  the  ramus  should  not  be  described  as  a 
separate  border,  as  it  is  merely  a  continuation  of  the  basilar 
border  of  the  body.  Where  it  joins  with  the  posterior  border 
of  the  ramus  the  bone  is  twisted  so  as  to  be  everted,  and 
forms  a  prominent  projection,  which  varies  greatly  with  the 
individual  on  either  side  of  the  face.     This  angle  of  the  jaw  is 


86  DESCRIPTIVE  ANATOMY. 

roug-hened  for  muscular  attachment.  The  superior  border 
consists  of  two  projections,  an  anterior  and  posterior  with  an 
intervening-  notch,  the  sigmoid.  Of  these  projections  the  ante- 
rior is  called  the  Coronoid  Process,  while  the  posterior  is  de- 
scribed as  the  Condyle  of  ih.Qjazv,  the  notch  between  the  two 
being-  called  the  Sigmoid.  The  Coronoid  Process  is  thin, 
triang-ular  in  outline;  presents  an  anterior  border,  which  is 
continuous  with  the  outer  lip  of  the  g-roove.  on  the  anterior 
border  of  the  ramus,  a  posterior  thinner  and  sharper  border, 
continuous  with  the  sigmoid  notch,  and  a  blunt  point,  the 
extremity,  which  is  received  into  the  fibres  of  the  Temporal 
muscle.  The  sigmoid  notch  is  concave  from  before  backward, 
its  edg-e  thin  and  sharp.  Behind  this  comes  the  condyle, 
which  consists  of  a  convex,  oval  articular  surface,  mounted 
upon  a  constricted  portion  of  the  bone,  called  the  "neck." 

This  condyle  is  oblique  in  its  direction,  its  long-  diameter 
being  from  without  inward  and  backward.  It  is  articular  further 
down  behind  than  in  front  ;  and  fits  into  the  Glenoid  cavity, 
which  is  found  on  the  inferior  surface  of  the  squamous  por- 
tion of  the  temporal  bone.  The  neck  of  the  condyle,  constric- 
ted antero-posteriorly,  extends  laterally,  so  that  the  condyle 
seems  to  rest  on  two  abutments,  one  from  either  side.  In  front 
and  to  the  inner  side  is  found  a  deep  depression  beneath  each 
condyle.  As  life  advances  the  obliquity  with  which  the 
ramus  of  the  bone  ascends  increases,  so  that  in  extreme  old  ag-e 
it  nearly  prolong-s  the  direction  of  the  body.  This,  however, 
is  not  due  to  a  change  in  the  direction  of  the  bone  ;  but  to  the 
loss  of  the  teeth,  and  the  consequent  absorption  of  the  alveolar 
process. 

The  Articulated  Skull. 

The  articulated  skull  is  produced  by  the  union  of  the  bones 
of  the  cranium  and  the  bones  of  the  face.  A  description 
of  the  articulations,  known  as  sutures,  will  be  found  under 
the  head  of  articulations  in  g-eneral. 

The  skull  is  divisible  into  five  reg-ions:  superior,  inferior, 
anterior  and  two  lateral. 


OSTEOLOGY.  8/ 

Superior  Region. 

The  superior  reg^ion  or  vertex,  is  bounded  in  front  by  the 
frontal  eminences,  on  each  side  by  the  temporal  ridg^e,  and  be- 
hind by  the  posterior  occipital  protuberance  and  the  superior 
curved  lines  of  the  occipital  bone.  It  is  formed  by  part  of  the 
frontal  bone,  most  of  the  parietal  bones  and  a  part  of  the  oc- 
cipital bone.  It  is  divided  into  a  superior  and  an  inferior 
aspect. 

The  superior  surface  is  seen  to  be  crossed  transversely  by 
the  coronal  suture,  extending-  backward  from  the  centre  of 
which  is  the  sagfittal  suture,  which  terminates  posteriorly  in 
the  lambdoid  suture.  The  parietal  'foramen  may  be  seen  on 
each  side  of  the  sag-ittal  suture  near  its  posterior  extremity. 
On  each  side  is  seen  the  parietal  eminence.  This  surface  is 
markedly  convex. 

The  inferior,  or  cerebral  surface,  is  concave,  and  presents 
the  following-  appearances:  on  the  frontal  bone,  in  the  middle 
line,  is  seen  the  indistinct  commencement  of  a  g-roove,  for  the 
superior  long-itudinal  sinus,  which  passes  backward,  growing- 
broader  and  more  distinct  as  it  travels,  first  along-  the  line  of 
union  of  the  parietal  bones  and  then  down  the  superior  limb 
of  the  occipital  cross  to  terminate  at  the  anterior  occipital 
protuberance;  along-  the  edg-es  of  this  g-roove  are  seen  several 
pits  for  lodg-ing-  the  Pacchionian  bodies,  and  external  to  these 
dig-ital  pits  for  the  convolutions  of  the  brain;  numerous  arbo- 
rescent arterial  furrows  are  also  seen. 

Lateral  Region. 

The  lateral  reg-ion  is  subdivided  into  four  portions — mastoid, 
tem.poral,  zyg-omatic  and  spheno-maxillar}-. 

Mastoid  Portion. 

The  mastoid  portion  of  the  lateral  reg-ion  extends  backward 
from  the  eminentia  articularis,  and  in  it  are  seen  the  following- 
appearances:  the  mastoid  foramen  and  process;  the  external 
auditory  meatus;  the  auditory  process,  the  g-lenoid  fossa,  which 
is  bounded  above  by  the   posterior  root  of  the  xyg-oma,   behind 


88  DESCRIPTIVE  ANATOMY. 

by  the  middle  root  and  vag-inal  process,  and  in  front  by  the 
anterior  root  of  the  zygoma.  It  is  crossed  transversely  by  the 
fissure  of  Glaser,  the  surface  in  front  of  the  fissure  being- 
articular  and  that  behind  rough;  where  the  roots  of  the  zygoma 
meet  is  the  tubercle. 

Temporal  Portion. 

The  temporal  portion  of  the  lateral  region  is  also  called  the 
temporal  fossa.  Its  upper  and  posterior  limit  is  the  temporal 
ridge;  this  ridge  commences  at  the  external  angular  process  of 
the  frontal  bone  and  curving  upward  and  backward,  leaves 
the  frontal  and  passing  across  the  parietal  bone,  arches 
downward  over  the  squamous  portion  of  the  temporal  bone  and 
terminates  in  the  posterior  root  of  the  zygoma.  In  front  of 
the  temporal  fossa  is  the  external  angular  process  of  the  frontal 
bone  and  the  malar  bone.  Below,  it  terminates  at  the  zygoma 
without  and  the  pterygoid  ridge  within.  Its  constituents  are 
furnished  by  the  frontal  bone,  the  malar  bone,  the  greater  wing 
of  the  sphenoid  the  parietal  bone  and  the  squamous  portion  of 
the  temporal  bone. 

Zygomatic  Portion. 

The  zygomatic  portion  of  the  lateral  region  is  situated  below 
the  temporal  portion  and  is  bounded  above  by  the  lower  surface 
of  the  greater  wing  of  the  sphenoid,  the  pterygoid  ridge  and 
the  squamous  portion  of  the  temporal  bone;  \n  front  by  the 
posterior  surface  of  the  superior  maxilla  and  by  the  malar; 
internally  by  the  external  pterygoid  plate  and  pterygo- 
maxillary  fissure;  externally,  by  the  zygoma  and  the  ramus  of 
the  inferior  maxilla.  In  this  region  are  seen  two  fissures, 
one  horizontal,  the  spheno-maxillary,  and  one  vertical,  the 
pterygo-maxillary,  the  one  being  at  right  angle  to  the 
other.  The  spheno-maxillary  fis«ure  is  seen  by  looking-  into 
the  orbit;  it  is  situated  at  the  lower  part  of  its  outer  wall 
posteriorly,  betw^een  the  greater  wing  of  the  sphenoid  above 
and  the  orbital  plate  of  the  superior  maxilla  below,  terminating, 
frequently,  in  the  malar  bone  anteriorly;  the  posterior  termina- 
tion is  at  the  point  where  the  pterj^go-maxillary  fissure  begins, 
which  descends  between  the  tuberosity  of  the  superior  maxillary 
in  front  and  the  pterygoid  process  behind. 


OSTEOLOGY.  89 

Spheno-Maxillary  Fossa. 

At  the  point  of  junction  of  the  two  fissures  is  a  small  fossa, 
the  size  of  the  end  of  the  little  fingfer,  called  the  spheno-max- 
illary  fossa  ;  it  is  thus  formed  :  above  is  the  flat  surface  just 
at  the  base  of  the  pteryg'oid  process  anteriorly  ;  behind  is  the 
pteryg-oid  process,  in/ro;^/is  the  superior  maxilla;  internally 
is  the  perpendicular  plate  of  the  palate  bone.  There  arey^z-e 
foramina  foiDid  \w  this  fossa.  Three  of  them  are  found  on 
the  upper  posterior  wall,  i.  e.,  on  the  flat  surface  at  the  base 
of  the  pteryg-oid  process  ;  they  are — 1st,  foramen  rotiindum  ; 
2nd,  pter}\^oid,  or  Vidian  \  2vdi,ptery§'o-palatine ',  on  tho^  in )ier 
wall  is  seen  the  4th,  spheno-palatine\  and  5th,  iiiferiorly,  is  seen 
the  opening-  into  the  posterior  palatine  canal,  with  accessory 
posterior  palatine  canals. 

Takingf  the  lateral  reg-ion  of  the  skull  as  a  whole,  it  may  be 
seen,  from  the  foregfoing  description,  that  it  is  triang-ular  in 
outline  and  is  bounded  as  follows ;  the  base  is  represented  by 
the  sweep  of  the  temporal  ridg-e  ;  the  apex  is  at  the  ang-le  of 
the  inferior  maxilla  ;  the  sides  may  be  represented  by  two  lines, 
meeting-  at  the  ang-le  of  the  inferior  maxilla,  the  one  drawn 
from  the  external  ang-le  of  the  frontal  bone  and  the  other  from 
the  mastoid  process.  The  bones  entering-  into  its  formation 
are  ;  the  mastoid  and  squamous,  and  the  base  of  the  petrous 
portions  of  the  temporal  bone  ;  part  of  the  frontal  bone  ;  part 
of  the  g-reater  wing-  of  the  sphenoid,  part  of  the  parietal,  part 
of  the  malar,  and  the  constituents  of  the  spheno- maxillary 
fossa,  as  g-iven  above. 

The  Inferior  Region  of  the  Skull. 

The  Inferior  Reg-ion,  or  Base,  of  the  Skull,  presents  two 
surfaces,  superior  and  inferior,  or  cerebral  and  basilar. 

The  Inferior  Surface  is  bounded  in  front  by  the  alveolar 
process  of  the  superior  maxillary  ;  and  from  the  tuberosity  of 
the  superior  maxilla  it  is  limited  by  an  imaginary  line,  which, 
extending-  by  the  styloid  process  of  the  temporal  bone,  passes 
back  to  the  superior   curved   line  of  the  occipital,  and   ends  at 


90  DESCRIPTIVE  ANATOMY. 

the  posterior  occipital  protuberance.  [In  describiag"  the  appear- 
ances found  on  this  face  of  the  skull  it  is  much  more  accurate 
to  begfin  with  those  on  tlie  mid-line  of  the  body,  which  are  sin- 
gle appearances,  while  the  double  appearances  can  be  given 
later.]  Commencing-  on  the  mid-line  we  find  extending  from 
before  backward  a  foramen,  called  the  Anterior  Palatine. 
Behind  this  foramen  is  the  suture  between  the  two  horizontal 
plates  of  the  two  superior  maxillary  bones,  and  behind  this 
again  the  suture  between  the  two  horizontal  plates  of  the  two 
palate  bones.  This  suture  terminates  in  the  posterior  palatine 
spine,  while  above  and  behind  this  spine  is  the  concave  free 
border  of  the  vomer.  Behind  this  comes  the  pharyngeal  ridge 
of  the  basilar  process  of  the  occipital,  which  leads  to  the  fora- 
men magnum,  beyond  wdiich  is  found  the  vertical  limb  of  the 
Occipital  cross,  which  terminates  in  the  posterior  occipital  pro- 
tuberance. On  either  side  the  following  appearances  will  be 
noted  :  in  front,  the  rough  inferior  surface  of  the  palatine  pro- 
cess of  the  superior  maxilla,  behind  which  lies  the  suture  be- 
tween this  process  and  the  horizontal  plate  of  the  palate  bones  ; 
behind  this  the  nasal  cavity,  and  on  the  outer  side  of  the  nasal 
cavity,  the  pterygoid  process  and  pterygoid  fossa  of  the  sphe- 
noid. Behind  the  pterygoid  process  is  the  middle  lacerated 
foramen;  external  to  that  is  the  foramen  ovale;  external  to 
this  the  foramen  spinosum  ;  external  to  that  the  spine  of  the 
sphenoid  ;  and  then  the  appearances  seen  on  the  inferior  sur- 
face of  the  petrous  portion  of  the  temporal  bone.  The  infe- 
rior surface  of  the  petrous  portion  of  the  temporal  exhibits  as 
the  most  internal  appearance  a  rough,  quadrilateral  projection 
of  bone.  Behind  and  external  to  this  is  the  aperture  of  en- 
trance for  the  carotid  artery  ;  external  to  and  behind  this  a 
thin  elongated  projection  of  bone,  called  here  the  Vaginal 
Process.  Internal  to  this  is  the  foramen  laceriim  posterius  ; 
and  in  the  interval  between  the  posterior  lacerated  foramen 
and  the  carotid  aperture  of  entrance  is  a  thin  sheet  of  bone 
marked  by  two  minute  apertures,  the  one  for  the  transmission 
of  Jacobson's  and  the  other  for  the  transmission  of  Arnold's 
nerve.     The  Vaginal   process,  as  it  passes   upward  and  back- 


OSTEOLOGY.  91 

ward,  divides  to  enclose  the  next  appearance,  which  is  the 
st3'loid  process,  while  next  to  the  styloid  process  is  a  foramen, 
the  stylo-mastoid  foramen.  Still  further  behind  is  a  narrow 
fissure  between  the  vag-inal  and  mastoid  processes  called  the 
Auricular  Fissure,  while  internal  to  the  mastoid  process  is 
another  and  larg-er  depression,  known  as  the  Dig-astric  Fossa, 
and  internal  to  that  a  depression  called  the   Occipital  Groove. 

We  next  encounter  the  appearances  on  the  occipital  bones; 
viz.,  the  condyles,  with  condyloid  fossae  behind,  and  in  the  bot- 
tom of  the  fossae  the  opening's  of  the  posterior  condyloid  fora- 
miaa,  when  these  foramina  are  present.  In  front  on  either 
side  of  the  condyle  is  seen  the  anterior  condyloid  foramen. 
Behind  these  appearances  is  the  roug-hened  posterior  surface 
of  the  occipital  bone  as  far  upas  its  superior  curved  line. 

In  describing-  the  appearances  on  the  base  of  the  skull,  it  is 
necessary  to  g-ive  not  only  those  appearances,  btit  their  bound- 
aries as  well.  Thus  the  tivo  posterior  nares  are  bounded, 
each  internally  by  the  posterior  border  of  the  vomer,  externally 
by  the  inner  surface  of  the  internal  plate  of  the  pteryg-oid  pro- 
cess, above  by  the  expanded  ala  of  the  vomer,  and  external  to 
this  the  vaginal  process  of  the  sphenoid.  Below  they  are 
bounded  by  the  posterior  concave  free  border  of  the  horizontal 
plate  of  the  palate.  The  middle  lacerated  foramen  is  bounded 
internally  by  the  basilar  process  of  the  occipital  bone,  extern- 
ally by  the  apex  of  the  petrous  portion  of  the  temporal;  in 
front  it  is  bounded  by  the  posterior  border  of  the  upper  sur- 
face of  the  g-reater  wing-  of  the  sphenoid.  In  this  foramen 
may  be  seen  the  opening-  of  the  Vidian  canal,  leading-  to  the 
termination  of  that  canal  in  the  spheno-maxillary  fossa.  Pos- 
teriorly it  is  limited  by  the  junction  of  the  anterior  border  of 
the  temporal  with  the  basilar  process  of  the  occipital.  To  the 
outer  side  of  the  middle  lacerated  foramen  can  be  distinctly 
seen  the  space  between  the  squamous  and  petrous  portions  of 
the  temporal,  in  which  are  lodged  the  two  canals,  the  upper 
for  the  tensor  tympani,  the  lower  for  the  Kustachian  tube, 
separated  from  each  other  by  a  thin  process  of  bone,  called  the 
Processus    Cochlcariformis   (Iv.    Cochleare,   a  spoon;  forma, 


92  DESCRIPTIVE  ANATOMY. 

shape).  T\\Q,  posterior  lacerated  foramen  is  bounded  in  front 
by  the  posterior  border  of  the  petrous  portion  of  the  temporal, 
and  behind  by  the  junction  of  the  basilar  process  with  the  infe- 
rior border  of  the  occipital,  these  two  bones  presentino-  notches, 
which  when  articulated  tog-ether  form  the  Posterior  Lacerated, 
or  Jugular,  Foramen. 

The  Superior  Surface  of  the  Base  of  the  Skull. 

The  Superior  Surface  of  the  Base  of  the  Skull  presents  in 
front  the  foramen  caecum,  behind  this  the  crista  g"alli,  behind 
the  crista  galli  the  articulation  between  the  ethmoidal  spine  of 
the  sphenoid  and  the  sphenoidal  notch  of  the  ethmoid,  behind 
that  a  transverse  ridge  slightly  formed  bounding  the  optic 
groove  in  front.  Next  is  the  groove  itself;  and  behind  that  is 
its  posterior  boundary,  the  olivary  process.  Behind  the  olivary 
process  is  a  deep  depression  on  the  upper  surface  of  the  sphe- 
noid, the  Sella  Turcica  (Iv.  A  Turkish  saddle),  behind  the 
sella  turcica  the  Dorsum  Ephif)pii  (L.  The  back  of  a  horse- 
cloth), behind  that  the  Clivus  BlumenbaclufLt.  C/eV?^^",  a  slope), 
leading  to  the  grooved  upper  surface  of  the  basilar  process  of 
the  occipital  bone.  Behind  the  Clivus  Blumenbachii  is  the 
foramen  mag-num,  behind  this  the  vertical  limb  of  the  occipi- 
tal cross,  and  at  the  termination  of  the  upper  surface  of  the 
base  of  the  skull  the  anterior  occipital  protuberance. 

To  describe  the  lateral  appearances  more  intelligently  it  is 
necessary  to  divide  this  portion  of  the  skull,  which  is  so  irregu- 
lar in  outline,  into  three  foss^.  These  are  known  as  the 
anterior,  middle  and  posterior  ;  and  they  descend  like  steps, 
the  anterior  being  the  highest,  the  middle  next,  and  the  poste- 
rior the  lowest.  '^\\Q^  anterior  fossa  oi  the  skull  is  bounded 
in  front  by  the  junction  of  the  horizontal  and  vertical  portions 
of  the  frontal  bone  ;  behind,  in  the  mid-line,  by  the  optic 
ridge,  on  either  side  of  which  we  have  the  posterior  borders 
of  the  lesser  wings  of  the  sphenoid.  Laterally  this  surface  is 
limited  by  the  vertical  portion  of  the  frontal  bone.  The 
middle  fossa  has  for  its  anterior  boundaries  the  posterior 
boundaries  of  the  anterior  fossa  ;  viz.,  the  orbital  ridge  in  the 
centre  and  the   posterior   border  of   the  lesser  wings  of  the 


OSTEOLOGY.  93 

Sphenoid  laterally.  Posteriorly  it  is  bounded  in  the  mid-line 
by  the  basilar  suture,  laterally  by  the  upper  border  of  the 
petrous  portion  of  the  temporal.  The  f)osterior  fossa  is 
bounded  in  front  by  the  basilar  suture,  on  either  side  by  the 
upper  border  of  the  petrous  portion  of  the  temporal,  behind 
in  the  mid-line  by  the  anterior  occipital  protuberance,  and  on 
either  side  of  that  by  the  lateral  limbs  of  the  occipital  cross. 
The  bones  entering-  into  the  formation  of  the  anterior  fossa 
are  the  orbital  plates  of  the  frontal,  the  cribriform  plate  and 
crista  g-alli  of  the  ethmoid,  the  upper  surface  of  the  lesser 
wing's  of  the  sphenoid,  and  the  anterior  one-third  of  the  upper 
surface  of  the  body  of  the  sphenoid.  Those  which  form  the 
middle  fossa  are  the  posterior  two- thirds  of  the  upper  sur- 
face of  the  body  of  the  sphenoid,  the  whole  upper  surface  of 
the  greater  wing-  of  the  sphenoid,  the  anterior  face  of  the 
petrous  portion  of  the  temporal,  and  the  internal  face  of  the 
squamous  portion  of  the  temporal.  Those  bones  which  form 
the  -posterior  fossa  are  the  posterior  surface  of  the  petrous 
portion  of  the  temporal,  the  postero-inferior  ang-le  of  the 
parietal,  and  all  of  the  anterior  surface  of  the  occipital  which 
lies  below  the  transverse  g-roove  for  the  lateral  sinuses  upon 
that  bone.  The  appearances  in  the  anterior  fossa  are  the 
foramen  caecum,  the  crista  gfalli,  the  ethmoidal  spine  of  the 
sphenoid  and  its  articulation  with  the  sphenoidal  notch  of  the 
ethmoid  and  the  optic  ridg-e  forming-  one  of  its  boundaries.  On 
the  mid-line  of  the  frontal  bone  is  seen  the  beg-inniug-of  the  long-i- 
tudinal  sinus.  The  lateral  appearances  are  the  g-rooves  which 
are  found  upon  the  upper  surface  of  the  cribriform  plate  of  the 
ethmoid,  including-  the  slits  for  the  nasal  nerves.  Still  further 
external  is  the  irreg-ular  upper  surface  of  the  orbital  process  of 
the  frontal,  three  rows  of  foramina  on  the  upper  surface  of  the 
ethmoid,  and  the  internal  opening-s  of  the  anterior  and  posterior 
ethmoidal  foramina.  In  the  middle  fossa  are  seen  the  optic 
g-roove,  the  olivary  process,  and  the  sella  turcica,  with  the 
dorsum  ephippii  upon  the  mid-line  extending-  to  the  basilar  su- 
ture, forming-  the  line  of  separation  between  the  middle  and 
the  posterior  fossai.      Laterally  are  seen    in  front  the  optic 


94  DESCRIPTIVE  ANATOMY. 

foramina,  the  anterior  clinoid  process,  behind  and  external  to 
this  along-  the  olivary  ridg-e  the  middle  clinoid  process,  ex- 
ternal to  and  slig-htly  in  front  of  this  the  anterior  lacerated 
foramen,  behind  and  external  to  that  the  foramen,  rotundum, 
still  further  behind  and  still  further  external  the  foramen 
ovale,  and  behind  and  external  to  that  the  foramen  spinosum, 
while  internal  to  this  external  row  of  foramina  is  the  italic- 
f-shaped  g-roove  for  the  carotid  sinus,  on  the  lateral  aspect  of 
the  body  of  the  sphenoid. 

Behind  this  is  the  upper  opening  of  the  middle  lacerated  fora- 
men, external  to  which  are  the  appearances  seen  on  the  anterior 
face  of  the  petrous  portion  of  the  temporal,  presenting-  from 
within  outward  the  digital  pit,  the  g-roove  leading  to  the  hiatus 
Fallopii,  the  petrosal  g-roove,  the  bulge  corresponding  to  the 
superior  semi-circular  canal,  and  the  depression  which  corre- 
sponds to  the  tympanum  and  the  orifice  of  the  carotid  canal. 
^\\Q.  posterior  fossa  presents  the  inclined  plane  formed  by  the 
grooved  upper  surface  of  the  occipital,  the  foramen  mag-num, 
and  the  lower  vertical  limb  of  the  occipital  cross.  lyaterally 
are  seen  the  appearances  on  the  posterior  surface  of  the  petrous 
portion  of  the  temporal;  viz,  the  internal  auditory  meatus,  the 
opening-  for  the  aqueduct  of  the  vestibule,  and  occasionally  a 
small  depression  for  lodging  a  process  of  the  dura  mater,  the 
posterior  border  of  the  petrous  portion  of  the  temporal,  aiding 
in  the  formation  of  the  jugular  foramen,  marked  by  the 
triangular  projection  of  bone  which  divides  this  foramen  into 
two  portions.  External  to  this  is  the  groove  which  enters  into 
the  formation  of  the  lateral  sinus;  and  which  commences  at 
the  jugular  foramen  on  the  jugular  process  o  E  the  occipital  bone, 
leaves  that  for  the  internal  face  of  the  mastoid  portion  of  the 
temporal,  leaves  that  bone  to  appear  momentarily  on  the 
postero-inferior  angle  of  the  parietal,  and  then  re-appears  upon 
the  occipital  bone,  where  it  forms  the  superior  boundary  of 
the  posterior  fossa  and  terminates  in  the  torcular  Herophili, 
to  the  side  of  the  anterior  occipital  protuberance.  In  the  fora- 
men magnum  can  be  seen  the  posterior  openings  into  the 
condyloid  foramina.  Below  the  lateral  limbs  of  the  occipital 
cross  are  the  fossae  which  lodg-e  the  cerebellum. 


OSTEOLOGY.  9o 


The  Anterior  Region  of  the  Skull. 

The  Anterior  Region  of  the  SkulU  or  Face,  is  bounded 
above  by  the  supercfliary  ridg-es,  below  by  the  basilar  border 
of  the  inferior  maxilla,  and  laterally  by  a  line  drawn  from  the 
external  ang-ular  process  of  the  frontal  bone  throug-h  the 
auo-le  of  the'inferior  maxilla.  It  presents  for  examination  five 
cavities  :  two  orbital,  two  nasal,  and  the  oral. 

The    Oral,  or   Buccal   Cavity,   has   been   already  described 
with  the  base  of  the  skull  and  with  the  inferior  maxilla  itself. 
In  the  recent  state  other  appearances  than  those  named  should 
be  mentioned  ;  but  these  are  not  seen  in  the  dry  preparation. 
The  Nasal  Cavity,  presenting"  its  anterior  aperture  on  the 
face,  is  bounded  above  by  the  lower  end  of  the  two  nasal  bones, 
on  either  side  by  the  anterior   border  of   the   nasal   process  of 
the  superior  maxilla,  below  by  the  concave  sharp  free  border 
of  the  horizontal  or  palate   process  of  the  superior  maxilla. 
Internally  each  cavity  is  bounded    by  a  triangular  aperture, 
which  in  the  recent  subject  is  filled  by  a  cartilag-e  of  similar 
shape,  but  which  in  the  prepared  skeleton  shows  only  the  an- 
terior border  of  the  vomer  and  the  anterior  border  of  the  per- 
pendicular  lamella  of  the  ethmoid.     These  cavities,  when  ex- 
amined  from  in  front,  exhibit  two  shelf-like   projections,  the 
inferior  and  middle  turbinated  bones.   The  inferior  turbinated 
bone  is    a    separate    bone,   while    the  middle  is  a   projection 
from  the  lateral   mass  of  the  ethmoid.     Between  the  inferior 
turbinated,  which  curls  over  in  the  cavity,  and  the  upper  sur- 
face of  the  palate  process  of  the  superior  maxilla  and  the  hori- 
zontal plate  of  the  palate  bone  is  a  narrow  long-  opening,  lead- 
in<,^  to  the  posterior  nares,  called  the  inferior  meatus  of  the  nose. 
Between  the  inferior  and  middle  turbinated   bones  is  a  second 
canal  of  the  same  shape  and  character,  thoug-h  smaller  in  size, 
called  the  Middle  Meatus  of  the  Nose.     The  superior  meatus. 
an  opening-  which  lies  between  the  superior  and  the  middle 
turbinated  bones,  is  smaller  in  size  and  more  oblique  in  direc- 
tion than  the  inferior  and  middle.     It  is  bounded  above  by  the 
superior  turbinated  and  below  by  the  inferior  turbinated  bone , 


96  DESCRIPTIVE  ANATOMY. 

hoth  of  them  portions  of  the  later:il  miss  of  the  ethmoid;  and 
of  course  belong-s  more  especially  to  the  ethmoid  bone  than  to 
the  cavity  of  the  nose.  The  middle  meatus  communicates 
anteriorly  by  a  tortuous  canal,  called  the  Iiifiindibulum ,  with 
the  anterior  ethmoidal  cells,  and  with  the  sinuses  of  the  frontal 
bone.  It  also  opens  into  the  antrum-maxillare.  Posteriorly 
the  superior  meatus  receives  by  the  spheno-palatine  foramen  a 
communication  with  the  spheno-maxillary  fossa,  while  in- 
directly it  extends  through  the  pyramid  of  Wister,  or  sphe- 
noidal turbinated  bone,  into  the  posterior  ethmoidal  sinuses, 
and  occasionally  into  the  body  of  the  sphenoid.  The  nasal 
cavities  are  more  completely  described  among-  the  soft  tissues. 
The  Orbital  Cavities.  Kach  orbit  is  an  irregular  four-sided 
pyramid,  having  of  course  four  surfaces  and  four  angles. 
The  apex  of  the  pyramid  is  directed  backward  and  inward  and 
the  base  forward  and  outward,  consequently  a  line  drawn 
through  the  centre  of  each  cavity  would  meet  that  of  the  oppo- 
site side  over  the  middle  of  the  sella  turcica,  passing  through 
the  optic  foramina.  The  sides  of  these  pyramidal  cavities  are 
superior,  inferior,  internal  and  external.  The  angles  are  su- 
pero-internal,  supero-external,  infero-internal  and  infero-ex- 
ternal.  These  lines  are  formed  by  the  articulations  of  the 
various  bones  which  enter  into  the  formation  of  the  cavities. 
The  supero-internal  line  is  formed  from  before  backward  by 
the  articulation  of  the  internal  angular  process  of  the  frontal 
bone,  and  the  upper  extremity  of  the  lachrymal  ;  behind  this 
by  the  superior  border  of  the  os  planum  of  the  ethmoid  and 
the  margins  of  the  rectangular  ethmoidal  notch  on  the  orbital 
plate  of  the  frontal  ;  behind  that  the  superior  surface  of  the 
orbital  process  of  the  palate  bone  articulating  with  the  sphe- 
noid. The  supero-external  ang-le  is  formed  by  an  irregular 
suture,  commencing  as  an  articulation  between  the  external 
angular  process  of  the  frontal  and  the  frontal  process  of  the 
malar.  Behind  this  is  the  orbital  process  of  the  malar  still 
articulating  with  the  frontal,  and  behind  that  the  superior  bor- 
der of  the  anterior  surface  of  the  greater  wing  of  the  sphenoid, 
articulating  with  the  orbital  process  of  the  frontal.  The  infero- 
internal  angle  is  formed   by  the  articulation  of  the  lower  ex- 


OSTEOLOGY.  97 

tremit}'  of  the  lachrymal  with  the  inner  border  of  the  orbital 
face  of  the  superior  maxilla  ;  behind  this  the  lower  border  of 
the  OS  planum  of  the  ethmoid  with  the  same  face  of  the  supe- 
rior maxilla;  and  behind  that  the  maxillary  surface  of  the  orbi- 
tal process  of  the  palate  with  the  ang-le  formed  by  the  junction 
of  the  internal  and  superior  surfaces  of  the  superior  maxilla. 
The  infero-cxterual  aiig-le  is  formed  by  the  suture  between 
the  maxillar}^  process  of  the  malar  and  the  malar  process  of 
the  superior  maxilla,  and  behind  these  by  the  spheno-maxillary 
fissure.  The  superior  xcall  is  formed  entirely  by  the  inferior 
surface  of  the  orbital  plate  of  the  frontal.  The  external  zjcill 
is  formed  jointly  by  the  internal  face  of  the  orbital  process  of 
the  malar,  and  the  anterior  surface  of  the  g-reater  wing-  of  the 
sphenoid.  The  inferior  face  is  formed  mainly  by  the  orbital, 
or  superior,  surface  of  the  superior  maxilla  ;  but  towards  its 
outer  side  the  grooved  portion  of  the  orbital  process  of  the 
malar  enters  into  its  formation.  The  most  posterior  portion 
of  the  inferior  face  is  formed  partly  by  the  orbital  process 
of  the  palate.  The  internal  face  is  formed  from  before 
backward  b}'  the  outer  surface  of  the  lachrymal,  the  outer 
face  of  the  os  planum  of  the  ethmoid,  and  behind  that 
by  the  orbital  face  of  the  orbital  process  of  the  palate 
bone.  Kntering-  into  this  cavity  are  two  foramina,  the 
anterior  and  posterior  ethmoidal,  which  establish  a  means 
of  communication  between  the  anterior  fossa?  of  the  skull 
and  the  cavity  of  the  orbit.  Posteriorly,  directly  at  its 
apex,  enters  the  foramen  opticiim,  and  below  this  is  seen 
the  anterior  lacerated  foramen,  formed  between  the  inferior 
border  of  the  lesser  wing"  of  the  sphenoid  and  the  posterior 
border  of  the  outer  surface  of  the  greater  wing-.  This  fora- 
men is  triangular  in  outline,  its  apex  directed  upward  and  out- 
ward, and  its  base  downward  and  inward,  and  communicates 
at  an  acute  angle  with  a  fissue  found  at  the  infero-external 
angle,  called  the  spheno-maxillary .  This  fissure  is  bounded 
above  by  the  lower  border  of  the  anterior  face  of  the  greater 
wing  of  the  sphenoid,  internally  by  the  postero-external  bor- 
der of  the  orbital  face  of  the  superior  maxilla.     Anteriorly  it 

Des  Anat— 7 


98  DESCRIPTIVE  ANATOMY. 

is  usually  bounded  b}^  the  non  articular  portion  of  the  poste- 
rior border  of  the  orbital  process  of  the  malar  ;  but  occasion- 
ally the  border  is  articular,  when  the  malar  does  not  enter 
into  the  formation  of  the  foramen.  On  the  external  wall  may  be 
seen  a  vertical  suture  extending-  between  the  posterior  border 
of  the  orbital  process  of  the  malar  and  the  external  border  of 
the  anterior  face  of  the  sphenoid.  Running"  throug-h  this  wall 
are  two  minute  foramina,  transmitting*  branches  of  the  fifth 
nerve,  called  the  tempero-nialar  foramina.  On  the  floor  of 
the  orbit,  near  its  posterior  extremity,  is  seenaslig-ht  g-roove, 
which  about  the  middle  of  the  floor  is  converted  into  a  foramen 
by  plung-ing-  beneath  the  orbital  surface  of  the  superior  max- 
illa. This  canal  continues  its  course  until  it  passes  beneath 
the  infraorbital  margfin,  and  terminates  on  the  anterior  sur- 
face of  the  face.  It  is  known  as  the  infraorbital  g-roove,  in- 
fraorbital canal  and  infraorbital  foramen  in  the  three  respec- 
tive places.  On  the  roof  of  the  orbit  is  seen  near  the  internal 
ang"ular  process  of  the  frontal  bone  a  sligfht  projection  or  some- 
times a  slig"ht  depression,  the  Fovea  Trochlearis.  External 
to  this  is  an  aperture  which  passes  throug'h  above  the  marg^in 
of  the  orbit,  and  is  known  as  the  supraorbital  foramen. 
I^xternal  to  this  and  just  behind  the  external  ang-ular  process 
is  the  most  depressed  portion  of  the  orbital  cavity,  forming-  a 
fossa  in  which  is  lodg-ed  the  lachrymal  g"land,  the  fossa  being- 
known  as  the  Fossa  Lachrymalis.  Below  the  orbit  is  the 
roug-hened  projection  of  the  malar  process  of  the  superior  max- 
illa, while  external  to  it  are  seen  the  external  opening-s  of  the 
tempero-malar  foramina.  Below  the  inferior  orbital  foramen 
is  a  depression,  called  the  Incisive  Fossa.  Above  the  orbits 
are  seen  the  supraorbital  ridg-es,  and  in  the  mid-line  the  nasal 
■prominence,  or  glabella.  Below  are  the  roug-hened  surfaces 
of  bone  for  the  attachment  of  the  various  muscles  of  expression. 

The  Nasal  Fossae. 

The  nasal  fosss  are  two  irreg-ular  cavities  situated  in  the 
face  and  extending-  from  the  anterior  to  the  posterior  nares. 
The  septum  between  the  two  is  formed,  above,  by  the  perpen- 
dicular lamella  of  the  ethmoid  bone,  in  its  lower  posterior  part, 


OSTEOLOGY.  99 

bs^  the  vomer  and  the  ang-ular  interval  left  between  the  two,  in 
front,  is  filled  in  by  a  triang-ular  plate  of  fibro-cartilag-e,  called 
the  cartilag-e  of  the  septum.  Each  fossa  presents  for  exami- 
nation /'o/^r  zualls.  The  inner  wall  is  formed  by  the  septum. 
The  outer  zvall  is  formed  by  the  superiormaxiUa,  t\\.Q  inferior 
turbinated,  the  lachrymal,  the  ethmoid,  the  palate  and  the 
internal  pterygoid  plate  oi  VclQ.  sphenoid.  The  roof 'vs>  formed 
by  the  nasal,  the  frontal,  the  ethmoid  and  the  body  of  the 
sphenoid.  The  /f  cor  is  formed  \r\.  front,  by  Wi<i  palate  process 
of  the  superior  maxilla  and  completed  behind  hy  the  horizontal 
plate  of  ihQ  palate  bone.  The  outer  wall  of  the  nasal  fossa  is 
very  uneven;  a  considerable  bulg-e  inward  is  produced,  throug-h- 
out  its  whole  length,  by  the  inferior  turbinated  bone,  and  the 
space  between  this  bone  and  the  floor  is  called  the  inferior 
meatus.  Above  the  inferior  is  the  middle  turbinated  bone,  a 
part  of  the  lateral  mass  of  the  ethmoid,  and  the  space  between 
these  two  is  known  as  the  middle  meatus.  In  the  upper  part  of 
the  inner  face  of  the  lateral  mass  of  the  ethmoid,  is  a  fissure  called 
the  superior  meatus,  situated  between  the  superior  and  middle 
turbinated  bones  of  the  ethmoid.  Opening-  into  each  fossa  are 
eight  apertures.  Into  the  superior  meatus  there  are  three 
openings:  1st,  the  opening  of  the  sphenoidal  cells;  2d,  the 
opening  from  the  posterior  ethmoidal  cells;  3d,  the  spheno- 
palatine foramen,  communicating  with  the  spheno-maxillary 
fossa.  In  the  middle  meatus  there  are  also  three  openings:  1st, 
the  opening  into  the  antrum  viaxillare ;  2d,  the  opening  into  the 
a)iterior  ethmoidal c^Ws,;  3d,  the  opening  from  \h^frontal sinus ; 
the  last  two  communicating  with  the  upper  front  part  of  the 
meatus  through  the  infuulibulum.  Into  the  inferior  meatus 
there  are  two  openings;  1st,  the  nasal  duct,  on  its  outer  wall, 
and  2d,  the  anterior  palatine  foramen,  on  the  floor.  Just 
pfjsterior  to  the  outer  wall  of  the  inferior  meatus  is  the  opening 
of  the  Eustachiaii  tube,  in  fresh  subject. 

Articulation  of  the  Bones  of  the  Skull — Occipital  Bone. 

The  occipital  bone  articulates  by  its  txvo  condyles  with  the 
Atlas;  by  its  superior  border  with  the  tzuo  parietal  bones, 
forming  the  lambdoid  suture,  by  the  outer  half  of  each  inferior 


100  DESCRIPTIVE  ANATOMY. 

border  with  the  posterior  border  of  the  rtiastoid  portion  of  the 
temporal  bone,  and  by  the  inner  half  with  the  posterior  border 
of  the  petrous  portion;  by  the  basilar  process  with  the  posterior 
surface  of  the  body  of  the  sphenoid  bone,  forming-  the  basilar 
suture. 

Parietal  Bone. 

The  parietal  bone  articulates  by  its  u-p-per  border  with  its 
fellow,  forming  the  sag-ittal  suture;  by  its  lozoer  border  with 
the  upper  part  of  the  semicircular  border  of  the  squamous 
portion  of  the  temporal  bone,  forming-  the  squamous  suture;  by 
li^ posterior  border  with  the  upper  border  of  the  occipital;  by  its 
anterior  border,  with  one-half  of  the  semicircular  border  of 
the  frontal,  forming-  one-half  of  the  coronal  suture;  by  its  ante- 
rior inferior  angle,  with  the  frontal  triang-le  of  the  sphenoid, 
i.  e. ,  the  upper  border  of  the  outer  surface  of  the  greater  wing" 
of  the  sphenoid;  by  its  posterior  inferior  angle,  with  the  upper 
border  of  the  mastoid  portion  of  the  temporal  bone. 

Frontal  Bone. 

The  frontal  bone  articulates  by  its  superior,  or  semicircular 
border  with  the  anterior  border  of  the  two  parietal  bones; 
by  the  posterior  border  of  each  orbital  plate  with  the 
lesser  wing-  of  the  sphenoid;  by  the  triang-ular  surface 
i.  e.,  the  sphenoidal  triang-le  of  the  frontal,  at  the  junc- 
tion of  the  straig-ht  and  semicircular  borders,  with  the 
upper  border  of  the  outer  surface  of  the  g"reater  wing*  of 
the  sphenoid;  by  the  circumference  of  the  ethmoinal  fissure 
with  the  lateral  and  anterior  borders  of  the  cribriform  plate 
of  the  ethmoid,  and  with  the  upper  surface  of  the  lateral  mass 
of  the  ethmoid;  by  the  nasal  notch  with  the  nasal  bones  and 
the  nasal  process  of  the  superior  maxillary;  by  the  nasal  spine 
with  the  crest  of  the  nasal  bones,  in  front,  and  with  the  upper 
part  of  the  anterior  border  of  the  perpendicular  lamella  of  the 
ethmoid,  behind;  by  the  internal  angular  process  w^ith  the 
lachrymal  bone;  by  the  external  ang-ular  process  with  the 
frontal  process  of  the  malar  bone,  and  by  the  part  just  behind 
this  with  the  orbital  process  of  the  malar. 


OSTEOLOGY.  101 

Temporal  Bone. 

Squamous  Portion. 

The  squamous  portion  articulates  by  the   upper  part  of  its 

semicircular  border  with  the  lower  border  of  the  parietal  bone; 

by  the  front  part  of  the  same  border  with  the  posterior  border 

of  the  outer  surface  of  the  greater  wnng-  of  the  sphenoid  ;  by 

the  lower  part  of  the  same  border  wdth  the  outer  part  of  the 

posterior  border  of  the  upper  surface  of  the  g-reater  wing-  of 

the  sphenoid  :  by  the  anterior  part  of  the  glenoid  fossa  wnth 

the   condyle  of  the  inferior  maxilla  ;   by  the  extremity  of  the 

zygomatic   process   with  the   zygomatic  process  of  the   malar 

bone. 

Mastoid  Portion. 

By  its  upper  border  with  the  posterior  inferior  angle  of  the 
parietal;  by  its  -posterior  border  with  the  outer  half  of  the 
lower  border  of  the  occipital  bone. 

Petrous  Portion. 

The  petrous  portion  articulates  by  its  posterior  border  with 
the  inner  half  of  the  lower  border  of  the  occipital  bone;  by  its 
anterior  border  with  the  middle  part  of  the  posterior  border 
of  the  upper  surface  of  the  greater  wing  of  the  sphenoid. 

Sphenoid  Bone. 

Body:  By  Wv^  posterior  surface  oi  the  body  with  the  basilar 
process  of  the  occipital;  by  the  ethmoidal  sfine  with  the 
sphenoidal  notch  of  the  cribriform  plate  of  the  ethmoid;  by 
the  crest  with  the  upper  part  of  the  posterior  border  of  the 
perpendicular  lamella  of  the  ethmoid;  by  the  surface  on  each 
side  of  the  crest  with  the  posterior  extremity  of  the  lateral 
mass  of  the  ethmoid,  through  the  medium  of  the  pyramid  of 
Wistar,  by  which  it  also  articulates  with  the  posterior  sur- 
face of  the  orbital  and  upper  surface  of  the  sphenoidal  process 
of  the  palate  bone;  by  the  rostrum  and  vaginal  prrcesses  with 
the  upper  border  of  the  vomer. 

Greater  Wing.  By  the  posterior  border  oi  its  upper  sur- 
face with  a  portion   of  the  anterior  border  of  the  petrous  por- 


102  DESCRIPTIVE  ANATONY. 

tion  of  the  temporal;  by  the  external  border  oi  the  superior  sur- 
face (or  the  posterior  border  of  the  external  surface)  with  the 
semi-circular  border  of  the  squamous  portion  of  the  temporal; 
by  the  superior  border  of  the  external  face  with  the  anterior 
inferior  ang-le  of  the  parietal,  and  with  the  outer  part  of  the 
sphenoidal  triang-le  of  the  frontal;  by  the  anterior  border  oi 
the  outer  face  with  the  posterior  border  of  the  orbital  process 
of  the  malar;  by  the  outer  -part  of  the  upper  border  of  the 
orbital  face  with  the  straig-ht  border  of  the  frontal  bone;  by 
Vae.  frojital  triang-le  lying"  just  internal  to  the  upper  border  of 
the  outer  surface  with  the  sphenoidal  triang-le  at  the  junction 
of  the  vertical  and  horizontal  plates  of  the  frontal. 

Lesser  Wing-.  By  its  anterior  border  with  the  posterior 
border  of  the  orbital  plate  of  the  frontal. 

Pterygoid  process.  By  its  anterior  border  with  the  poste- 
rior border  of  the  perpendicular  plate  of  the  palate;  by  the 
triangnlar  interval  between  the  lower  part  of  its  two  plates 
with  the  tuberosity  of  the  palate  ;  by  the  inner  side  of  its  base 
with  the  posterior  part  of  the  outer  surface,  and  posterior 
border  of  the  sphenoidal  process  of  the  palate. 

Ethmoid  Bone. 

Horizontal  Plate:  By  its  lateral  and  anterior  borders  with 
the  circumference  of  the  ethmoidal  fissure  of  the  frontal.  By 
crista  galli  with  anterior  border  of  ethmoidal  notch  forming* 
foramen  coecum.  By  the  spheniod  notch  with  the  ethmoidal 
spine  of  the  sphenoid. 

Perpendicular  Lamella:  By  the  upper  part  of  its  posterior 
border  with  the  crest  of  the  sphenoid  ;  by  the  lower  part  of 
\\j&  posterior  border  with  the  upper  part  of  the  anterior  border 
of  the  vomer  ;  by  the  upper  part  of  its  anterior  border  with 
the  nasal  spine  of  the  frontal ;  by  the  lower  part  of  its  ante- 
rior border  with  the  crest  of  the  nasal  bones. 

Lateral  Mass :  By  its  upper  surface  it  is  continuous  with 
the  lower  surface  of  the  horizontal  plate,  and  the  half  cells 
on  the  orbital  plate  of  the  frontal,  by  its  posterior  extremity 
with  the  anterior  face  of  the  body  of  the  sphenoid  bone,throug"h 
the  medium  of  the  pyramid  of  Wistar  ;  by  its  anterior  extreme 


OSTEOLOGY.  103 

ity  with  the  inner  face  of  the  lachrymal  bone  and  with  the 
inner  face  of  the  nasal  process  of  the  superior  maxillary  ;  by 
the  upper  border  of  the  os  planum  with  the  horizontal  plate, 
by  the  lower  border  of  the  os  planum  with  the  inner  border 
of  the  orbital  face  of  the  superior  maxillary  bone,  and  behind 
that  with  the  orbital  process  of  the  palate  bone  ;  by  the  pos- 
terior border  of  the  os  plamim  with  the  front  of  the  body  of 
the  sphenoid  ;  by  the  anterior  border  of  the  os  planum  with 
the  posterior  border  of  the  lachrymal  bone  ;  by  the  part  below 
the  OS  planum  with  the  inner  face  of  the  superior  maxillary 
bone  ;  by  the  unciform  process  with  the  ethmoidal  process  of 
the  inferior  turbinated  bone  ;  by  the  anterior  extremity  of  the 
middle  turbinated  bone  with  the  superior  turbinated  crest  of 
the  nasal  process  of  the  superior  maxillary  ;  by  the  poste- 
rior extremity  oi  the  middle  turbinated  bone  with  the  superior 
turbinated  crest  of  the  vertical  plate  of  the  palate  bone. 

Nasal  Bone. 

By  its  upper  border  with  the  nasal  notch  of  the  frontal 
bone  ;  bv  its  outer  border  with  the  nasal  process  of  the  supe- 
rior maxillary  ;  by  its  inner  border  with  its  fellow  ;  by  the 
crest  oi  the  two  bones,  above,  with  the  nasal  spine  of  the  fron- 
tal ;  below,  with  the  lower  part  of  the  anterior  border  of  the 
perpendicular  lamella  of  the  ethmoid. 

Superior  Maxillary. 

The  superior  maxillary  bone  articulates  by  its  body  and 
processes. 

Body :  By  the  lower  part  of  its  posterior  border  with  the 
front  of  the  tuberosity  of  the  palate  bone;  by  the  internal 
brjrder  of  its  orbital  surface,  from  before  backwards,  with 
the  lower  border  of  the  lachrymal  bone,  the  os  planum  of  the 
ethmoid  and  the  anterior  face  of  the  orbital  process  of  the 
palate  bone.  Antero-externally  the  orbital  face  articulates 
with  the  lower  border  of  the  orbital  process  of  the  malar;  by 
its  internal  face  the  body  articulates,  by  the  part  posterior  to 
the  aperture  of  the  sinus  with  the  anterior  border,  the  max- 
illary process  and  most  of  the  outer  surface  of  the  vertical 


104  DESCRIPTIVE  ANATOMY. 

plate  of  the  palate;  above  the  aperture  with  the  outer  surface 
of  the  lateral  mass  of  the  ethmoid,  below  the  os  planum;  be- 
low the  aperture  with  the  maxillary  process  of  the  inferior 
turbinated  bone  ;  in  front  of  the  aperture  with  the  projection 
on  the  anterior  border  of  the  lachrymal  and  the  lachrymal 
process  of  the  inferior  turbinated  ;  by  the  injerior  turbinated 
crest  with  the  anterior  extremity  of  the  inferior  turbinated. 

Malar  Process :  By  the  malar  process  with  the  maxillary 
process  of  the  Malar. 

Palate  Process:  By  the  inner  border  of  the  palate  process 
with  the  inner  border  of  the  opposite  palate  process  and  with 
the  anterior  part  of  the  lower  border  of  the  Vomer;  by  its 
posterior  bordeo  with  the  anterior  border  of  the  horizontal 
plate  of  the  palate. 

Nasal  Process :  By  its  upper  border  with  the  nasal  notch 
and  internal  ang-ular  process  of  the  frontal;  by  the  inner  ed^e 
of  its  posterior  border  with  the  anterior  border  of  the  lach- 
rymal and  by  the  lachrymal  tubercle  with  the  hamular  process 
of  the  lachrymal;  by  the  upper  part  of  its  internal  surface 
with  the  anterior  extremity  of  the  lateral  mass  of  the  ethmoid; 
by  the  superior  turbinated  crest  with  the  anterior  extremity 
of  the  middle  turbinated  bone;  by  its  anterior  border  with  the 
posterior  border  of  the  nasal  bone. 

Palate  Bone. 

The  palate  bone  articulates  by  its  two  plates.  By  its  pro- 
cesses and  tuberosity. 

The  Horizontal  P/«/^  articulates  by  its  inner  border  with  the 
opposite  bone  and  with  the  posterior  part  of  the  lower  border 
of  the  Vomer:  by  its  anterior  border  with  the  posterior  bor- 
der of  the  palate  process  of  the  superior  maxillary. 

The  Perpendicular  Plate  articulates  by  most  of  its  external 
surface,  its  anterior  border  and  maxillary  process  with  the  in- 
ner face  of  the  body  of  the  superior  maxillary,  behind  the  ap- 
erture into  the  antrum;  by  its  superior  turbinated  crest  ^NWh. 
the  posterior  extremity  of  the  middle  turbinated  bone;  by  its 
inferior  turbinated  crest  with  the  posterior  extremity  of  the 
inferior  turbinated  bone;  by  \t^  posterior  border  with  the  ante- 


OSTEOLOGY.  105 

rior  border  of  the  pteryg-oid  process  of  the  sphenoid;  by  the 
<niterior  face  of  the  tuberosity  with  the  lower  part  of  the 
posterior  border  of  the  body  of  the  superior  maxillary  and  by 
its  posterior  face  with  the  lower  part  of  the  anterior  edgfe  of  the 
two  pterygoid  plates  filling  in  the  gap  between  them;  by  the 
anterior  face  of  its  orbital  process  with  the  posterior  part  of 
the  internal  border  of  the  orbital  face  of  the  body  of  the  supe- 
rior maxillary  ;  by  its  internal  face  with  the  external  surface 
of  the  lateral  mass  of  the  ethmoid,  below  and  behind  the  os 
planum  ;  by  its  posterior  fice  with  the  front  of  the  body  of 
the  sphenoid,  through  the  pyramid  of  Wista.  By  the  upper 
surface  of  the  sp\\e)widal  process  with  the  lower  surface  of 
the  vaginal  process  of  the  sphenoid  ;  by  its  posterior  border 
and  the  posterior  part  of  its  outer  face  with  the  inner  side  of 
the  base  of  the  pterygoid  process  of  the  sphenoid. 

Vomer. 

The  vomer  articulates  by  its  borders. 

By  the  groove  on  its  upper  border  with  the  rostrum  of  the 
sphenoid  ;  by  its  alec  with  the  opposing  faces  of  the  vaginal 
process  and  lower  surface  of  the  body  of  the  sphenoid;  by  its 
louer  border,  posteriorly,  with  the  crested  inner  border  of 
the  horizontal  plate  of  the  palate  and  anteriorly  with  the 
crested  inner  border  of  the  palate  process  of  the  superior 
maxillary  ;  by  the  upper  part  of  the  anterior  border  with  the 
lower  part  of  the  posterior  border  of  the  perpendicular  plate 
of  the  ethmoid. 

Inferior  Turbinated  Bone. 

By  its  anterior  extremity  with  the  inferior  turbinated  crest 
of  the  superior  maxillary;  by  its  posterior  extremity  wnth  the 
inferior  turbinated  crest  of  the  palate  ;  by  the  lachrymal  pro- 
cess with  the  edges  of  the  lachrymal  sulcus  of  the  inner  face 
of  the  body  of  the  superior  maxillary  and  with  the  projection 
on  the  anterior  border  of  the  lachrymal;  by  the  maxillary  pro- 
cess with  the  lower  margin  of  the  aperture  of  the  antrum  ;  by 
the  ethnioidal process  with  the  unciform  process  of  the  ethmoid. 


106  DESCRIPTIVE  ANATOMY. 


Lachrymal  Bone. 

The  lachrymal  bone  articulates  by  its  upper  extremity  with 
the  internal  angular  process  of  the  frontal;  by  its  posterior 
border  with  the  anterior  border  of  the  os  planum;  by  its  lozuer 
extremity  with  the  front  part  of  the  internal  border  of  the  or- 
bital plate  of  the  superior  maxillary;  by  the  anterior  border 
with  the  inner  edg'e  of  the  posterior  border  of  the  nasal  pro- 
cess of  the  superior  maxillary  and  by  the  projection  from  the 
lower  end  of  this  border  with  the  edg^es  of  the  lachrymal  sul- 
cus on  the  inner  face  of  the  body  of  the  superior  maxillary  and 
with  the  lachrymal  process  of  the  inferior  turbinated  bone  and 
by  the  back  part  of  the  internul  surface  with  the  anterior 
extremity  of  the  lateral  mass  of  the  ethmoid. 

Malar  Bone. 

The  malar  bone  articulates  by  its  processes  and  by  the 
anterior  border  of  its  body,  which  articulates  with  the  anterior 
border  of  the  malar  process  of  the  superior  maxillary. 

By  the  Frontal  Process  with  the  external  angular  process 
of  the  Frontal. 

By  the  Maxillary  Process  with  the  malar  process  of  the 
superior  maxillary. 

By  the  Zyg-omatic  Process  w^ith  the  zygomatic  process  of  the 
temporal  bone. 

By  the  Orbital  Process ;  the  lozver  Z^oro'^r  articulates  with 
the  orbital  surface  of  the  superior  maxillary,  antero-externally; 
by  the  posterior  border,  with  the  outer  border  of  the  orbital 
plate  of  the  greater  wing  of  the  sphenoid;  and  by  the  iipper 
border  with   the  frontal  behind   the  internal   angular  process. 

Inferior  Maxillary  Bone. 

The  inferior  maxillary  bone  articulates  by  its  condyles  with 
the  anterior  part  of  the  glenoid  fossa  of  the  temporal  bone. 

The  Hyoid  Bone. 

The  hyoid  bone,  or  lingual  bone  is  placed  in  the  upper, 
front  part  of  the  neck  atthe  bis2  of  the  tongue.     It  isU  shaped 


OSTEOLOGY.  107 

and  lies  horiz;ontally,  being-  a  symmetrical  bone.  It  is  an 
isolated  bone,  but  is  connected  by  aligfamentous  cord,  on  either 
side,  with  the  styloid  process  of  the  temporal  bone;  occasion- 
ally this  cord  becomes  ossified  and  then  a  complete  bony  arch 
is  formed  between  the  two  temporal  bones  throuo-h  the  hyoid 
bone.  It  is  divided  for  study  into  a  body  and  four  cornua,  or 
projections.  The  body  presents  two  surfaces,  two  borders, 
and  two  extremities.  The  anterior  surface  looks  upward  and 
slig-htly  forward  and  presents  four  depressions,  separated  by 
a  crucial  ridge;  the  confluence  of  the  arms  of  the  ridg-e  produc- 
ing- a  prominence  called  the  tubercle.  The  posterior  face  looks 
downwards  and  slig-htly  backwards;  is  concave,  both  trans- 
versely  and  vertically,  presenting-  a  deep  concavity.  The  upper 
border  faces  backward  and  is  rounded  and  roug-h.  The  lower 
border  faces  forward,  is  protuberant  and  marked  by  musclular 
attachment.  The  extremity  is  oval  and  roug-hened  by  cartil- 
ag-inous  attachment.  The  g-reater  cornu  stands  backwards 
from  the  extremity  of  the  body,  on  either  side,  and  is  rounded, 
g-rows  smaller,  but  is  terminated  posteriorly  by  a  nodular  en- 
larg-ement.     It  is  slig-htl}^  flattened  vertically. 

The  lesser  cornu  is,  until  old  ag-e,  cartilag-inous;  it  is  a  mere 
nodule  of  cartilag-e,  hook  like  and  about  a  quarter  of  inch  long-; 
its  direction  is  upward,  backward  and  slig'htly  outward  and 
it  articulates  by  a  diminutive  joint  at  the  junction  of  the  bodv, 
and  g-reater  cornu.  It  becomes  calcified  and  its  joint  obliterated 
only  very  late  in  life. 


108  DESCRIPTIVE  ANATOMY. 


THE  LIGAMENTS. 

The  study  of  joints,  or  articulations,  is  the  study  of  the  re- 
lation between  bones,  more  particularly  of  the  surfaces  of  ap- 
position and  the  means  by  which  the  bones  are  held  tog"ether 
and  at  the  same  time  permitted  to  move  upon  one  another.  In 
the  study  of  osteology  it  has  been  seen  that  the  articular  sur- 
faces of  the  different  bones  present  widely  varying"  appear- 
ances;  upon  these  differences  depends  the  classification  of 
joints.  In  some  joints  the  opposing  surfaces  present  inter- 
locking, tooth-like  processes,  so  that  the  union  of  the  bones 
results  in  an  immovable  joint.  This  form  of  articulation  is 
called  synarthrosis. 

The  contiguous  surfaces  may  be  roughened,  showing  the 
attachment  of  ligamentous  fibres  passing  directly  between  the 
bony  faces  ;  or  the  fibres  may  have  been  attached  through  the 
medium  of  cartilage,  coating  the  bony  surfaces.  This  indi" 
cates  a  joint  in  which  motion  is  very  slight,  consisting  of  a 
twisting  of  the  ligimentous  fibres  ;  and  the  articulation  is 
known  as  amphiarthrosis. 

The  bony  surfaces,  lastly,  may  be  smooth  and  polished,  as 
a  result  of  mutual  friction — indicating  a  freely  movable  joint 
of  the  class  called  diarthrosis. 

The  three  classes  of  joints,  then  are — 1st,  Synarthrodial, 
or  immovable  joints  ;  2nd,  Amphiarthrodial,  or  partially  mov- 
able ;  and  3rd,  Diarthrodial,  or  freely  movable  joints. 

Besides  the  bones,  there  are  other  structures  which  contri- 
bute to  the  formation  of  a  joint,  as  follows  :  In  the  Amphiar- 
throdial and  Diarthrodial  joints,  the  bones  are  held  together 
by  ligaments.  In  the  Amphiarthrodial  these  not  only  pass 
from  bone  to  bone,  exterior  to  the  joint,  but  directly  between 
the  bones,  within  the  joint,  forming  what  are  called  interosse- 
ous ligaments.  In  the  Diarthrodial  joints,  as  a  rule,  no  liga- 
mentous fibres  are  attached  to  the  articulating  surfaces  of  the 
bones  ;  the  ligaments,  more  or  less  completely  surrounding- 


LIGAMENTS.  109 

the  joint,  are  attached  to  both  bones  beyond  the  articular  sur- 
faces. The  fibres  may  entirely  surround  the  joint  forming-  a 
capsular  lig-ament,  or  they  may  be  g-athered  into  separate  bun- 
dles. 

In  the  Diarthrodial  joints  the  opposing-  bony  surfaces  are 
coated  by  encrusting",  or  articular  cartilage,  which,  on  its  deep 
face,  is  firmly  attached  to  the  bone,  and  presents  a  perfectly 
smooth,  free  surface  towards  the  opposing  bone. 

In  order  to  lessen  friction,  and  render  motion  entirely  easy, 
diarthrodial  joints  possess  a  secreting-,  serous-like  membrane, 
called  the  synovial  membrane,  which  secretes  a  viscid,  glairy 
fluid,  called  synovia.  The  synovial  membrane,  in  very  early 
life,  is  said  to  be  a  closed  sac,  coating-  the  entire  joint ;  but 
soon  the  portion  covering  the  encrusting-  cartilage  is  worn 
awa3%  or  becomes  inconspicuous. 

If  joints  are  subject  to  very  frequent  motion,  the  effect  of 
friction  is  further  g-uarded  ag-ainst  by  a  plate  of  fibro-cartilage, 
called  the  interarticular  cartilag-e.  This  is  a  more  or  less  flat, 
circular  plate  of  cartilage  interposed  between  the  encrusting- 
cartilages  of  the  bony  surfaces,  and  attached  only  by  its  cir- 
cumference to  the  lig*aments.  When  this  exists  entire,  the 
joint  will  have  two  synovial  membranes,  but  occasionally  the 
plate  is  \vorn  throug-h  and  then,  the  two  membranes  communi- 
cating-, there  is  virtually  but  one. 

Synarthrodia!  Joints — 4  Kinds. 

The  immovable  joints  are  almost  confined  to  the  bones  of 
the  skull,  the  articulations  between  which  are  g-enerally  called 
sutures. 

There  are  several  varieties  of  suture  :  1st.  Dentate,  or  Ser- 
rate, in  which  edges  of  the  bones  present  interlocking-  processes, 
called  dentate  when  long  and  tooth-like,  and  serrate  when 
short,  like  the  teeth  of  a  saw.  2d.  Suture  by  Harmony, 
in  which  two  roug-hened  surfaces  come  in  contact,  as  the 
inner  border  of  the  palate  processes  of  the  two  superior  max- 
illary bones.  3d.  Schindylesis,  where  the  edg-e  of  one  bone  is 
received  in  a  groove  in  another,  as  the  articulation  between 
the   vomer  and  the  sphenoid.     4th.  Gomphosis,  where  a  bone 


110  DESCRIPTIVE  ANATOMY. 

is  received  into  a  corresponding-  cavity  in  another.  THis  term 
is  applied  to  the  union  between  the  teeth  and  their  sockets, 
and  is  really  no  articulation. 

DiartKrodial  Joints — 6  Kinds. 

The  diarthrodial  joints,  in  accordance  with  the  varying- 
shape  of  the  articular  surfaces  are  divided  into  six  varieties. 

1st.  Arthrodial,  formed  by  more  or  less  flat,  plane  surfaces, 
so  that  motion  is  much  restricted. 

2nd.  Hing-eor  trochlear,  or  cringlymoid,  characterized  by  the 
presence  of  a  pully  on  one  of  the  articular  surfaces.  In  this 
joint  motion  can  occur  as  a  rule,  in  only  two  directions. 

3d.  Condyloid ,  in  which  one  element  is  a  condyle,  the  other 
a  proper  receiving-  cavity.  These  joints  are  generally  capable 
of  very  free  movement. 

4th.  Saddle-shaped,  or  concavo-convex  joints,  or  joints  of 
reciprocal  reception,  where  both  surfaces  are  saddle-shaped 
and  mutually  interlock.  The  examples  of  this  form  of  joint 
are  sterno- clavicular,  trapezio- metacarpal  and  calcaneo- 
cuboid. 

5th.  Pivot,  or  trochoid  joints. — There  are  only  two  of  these, 
atlo-axoid  and  radio-ulnar.  The}"  present  an  osseo-ligament- 
ous  ring,  in  which  a  part  of  one  bone  is  received  ;  this,  in  the 
first  example,  acting  as  a  pivot  around  which  the  other  bone 
revolves  ;  while,  in  the  second  case,  it  rotates  on  its  own  axis. 

6th.  Bill  and  socket,  or  enarthrodial  joints. — These  present 
a  more  or  less  spherical  head,  as  one  contribution,  while  a  re- 
ceiving cavitj'  is  the  other.  The  two  important  examples  of 
this  variety  are  the  shoulder  and  hip,  in  both  of  w^hich  motion 
is  very  free. 

In  describing  a  joint,  the  following  heads  have  to  be  consid- 
ered : 

1st.  The  class  and  variet\^  2nd.  The  bony  contributions. 
3rd.  The  ligaments.  4th.  The  synovial  membrane.  5th. 
The  inter-articular  cartilage,  perhaps.  6th.  The  motions  of 
v,'hich  the  joint  is  capable.  7th.  The  muscles  which 
strengthen  the  joint,  if  an5^ 


LIGAMENTS.  Ill 

As  numerous  as  the  motions  seem  to  be.  they  can  all  be  re- 
ferred to  the  following-  : 

(a)  Gliding,  which  occurs  to  some  extent  in  all  diarthrodial 
joints,  but  is  peculiarls*  characteristc  of  the  arthrodial.  It 
consists  of  the  slippiag*  of  one,  m^ri  or  less,  flit  an.i  plane 
surface  on  another. 

(d)  Flexion — anovular  movement  of  a  segfrnent  of  the  body 
in  an  antero-pDsterior  vertical  plane,  generally  forward,  but 
in  some  cases  backward. 

(c)  Extension — the  reverse  of  flexion. 

(d)  Abduction — the  movement  of  a  segment  away  from  some 
established  mid  line,  generally  that  of  the  body. 

(e)  Adduction — the  reverse  of  abduction. 

(/")  Circumduction — the  partial  performance  in  rapid  and 
regular  succession  of  the  four  preceding  movements,  passing, 
in  inward  circumduction,  from  flexion  to  adduction,  to  exten- 
sion, to  abduction,  and  a'J-ain  to  flexion.  In  outward  circum- 
duction the  order  is  reversed.  In  the  performance  of  this 
movement,  the  moving  segment  circumscribes  a  coneshaped 
space,  the  apex  of  which  is  at  the  joint  and  the  base  at  the 
distal  extremity  of  the  moving  segment. 

(^)  Revolution,  or  false  rotation.  This  occurs  at  but  two 
joints,  the  atlo-axoid  and  radio  ulnar.  In  the  first  case,  the 
atlas  revolves  around  the  odontoid  process  as  an  axis  ;  in  the 
latter  the  radius  rotates  around  its  own  axis  in  the  ring  formed 
by  the  orbicular  ligament  and  the  lesser  sigmoid  cavity. 

(/^)  Rotation,  or  true  rotation.  This  is  almost  limited  to 
two  joints,  the  shoulder  and  the  hip,  and,  as  it  happens,  can 
be  defined  in  the  same  terms  for  both,  viz  :  movement  outward 
or  inward  around  a  line  drawn  from  the  innerm3st  point  of 
the  humerus  or  femur,  to  the  innermost  point  of  the  inner 
condyle  of  either  bone. 

6th.  A  statement  of  the  mechanism  of  motion — that  is,  of 
the  changes  which  occur  in  the  relative  positions  of  the  artic- 
ulating surfaces  during  the  performance  of  any  given  motion, 

7th,  The  muscles  which  are  in  contact  with  the  ligaments 
of  the  joint,  and  which  may  be  considered  as  imparting 
strength  to  the  articulation. 


112  DESCRIPTIVE  ANATOMY. 

8th.  In  the  important  joints,  the  arteries  and  nerves  distri- 
buted to  them. 

The  Articulations  of  the  Vertebral  Column. 

The  articulations  of  the  spinal  column  may  be  divided  intO' 
those  of  the  (1st)  Column  in  g-eneral;  (2d)  Atlo-axoid;  (3d) 
Occipito-atloid;  (4)  Sacro- vertebral. 

Articulations  of  the  Spine  in  General. 

E)ac-h  vertebra  articulates  with  the  vertebra  above  and  the 
one  below  by  a  joint  of  the  diarthrodial  class,  and  arthrodial 
variety,  on  each  side,  formed  by  the  inferior  and  superior 
articular  processes.  The  lig-aments  are  capsular  around  the 
articulating-  surfaces,  and  those  which  bind  the  same  seg-- 
ments  of  the  different  vertebrae  tog-ether.  These  ligaments 
are  collectively  known  as  the  common  lig-aments  of   the  spine. 

Articulation  of  the  Articular  Processes. 

The  articulation  between  contig-uous  articular  processes  is  a 
diarthrodial  joint  of  the  arthrodial  variety,  presenting-  a 
synovial  membrane  and  one  ligament,  an  imperfect  capsular 
ligament. 

The  Ligaments  of  the  Spine  in  General — Ligaments  of  the 

Bodies. 

The  bodies  of  the  vertebrae  are  connected  by  means  of 
intervertebral  disks  and  anterior  and  posterior  common  lig-a- 
ments.  The  intervertebral  disk  is  found  lying-  between  the 
opposing*  surfaces  of  two  adjacent  vertebrae,  firmly  adherent 
to  each.  In  shape  it  corresponds  exactly  with  the  bodies  be- 
tween which  it  lies;  in  thickness  it  varies  with  the  different 
reg-ions  of  the  spine.  Collectively,  the  disks  form  about  one- 
fourth  the  length  of  the  column  and  they  are  found  between 
all  the  bodies  except  the  first  and  second,  being  absent  there 
because  the  atlas  has  no  body.  It  is  formed  externally,  of  con- 
centric laminae  of  fibrous  tissue  and  fibro-cartilage,  the  centre 
of  the  disk  being  a  soft,  pulpy  mass. 

Some  of  the  fibres  extend  from  the  upper  surface  of  the 
vertebra  below  to  the  lower  surface  of  the  vertebra  above;  and 


LIGAMENTS.  113 

these  fibres  are  crossed  in  the  form  of  the  letter  X,  so  that 
when  the  body  bends  or  twists  to  either  side  the  cords  of  the 
fibres  ma}"  twist  or  untwist  as  the  occasion  demands. 

The  Anterior  Common  Ligament  is  found  descending-  along- 
the  front  of  the  bodies  from  the  axis  to  the  sacrum,  widening- 
as  it  descends.  As  a  matter  of  fact  this  ligament  extends  to 
the  basilar  process  of  the  occipital  bone;  but  it  has  been  custo- 
mary to  consider  the  upper  portion  extending-  from  the  axis 
to  the  occipital  bone  as  a  separate  lig-ament.  It  is  composed 
of  superimposed  la3^ers  of  fibres,  the  deepest  of  which  are  at- 
tached simply  to  the  bodies  of  adjacent  vertebrae,  while  the 
next  layer  of  fibres  extends  over  two  or  three  vertebrae,  and 
the  most  superficial  extends  over  four  or  five.  This  liga- 
ment w^idens  as  it  descends,  is  not  attached  over  the  centres 
of  the  bodies  of  the  vertebrae,  where  it  leaves  a  slig-ht  space 
between  itself  and  the  bodies,  but  is  attached  to  the  lips  of 
the  vertebrae  and  to  the  intervertebral  disks.  A  few  scattered 
fibres  continue  this  ligamentous  band  around  the  bodies  of  the 
vertebrae  to  the  transverse  processes. 

The  Posterior  Common  Lig-ament  lies  within  the  spinal 
canal  ;  and  is  attached  to  the  bodies  of  the  vertebrae,  extend- 
ing- from  the  axis  to  the  sacrum.  Just  as  is  the  case  with  the 
anterior  common  ligament,  this  in  reality  extends  to  the  cra- 
nium ;  but  the  upper  portion  of  it  is  known  under  a  separate 
name.  Like  the  anterior  it  consists  of  several  layers  of  fibres  ; 
but  unlike  that  lig-ament  it  narrows  as  it  descends  ;  and  instead 
of  having-  straig-ht  edg-es,  it  is  scalloped,  widening-  over  each 
intervertebral  disk  and  narrowing-  over  the  body.  It  is  thinner 
and  less  powerful  than  is  the  anterior  common  lig-ament. 

Ligaments  of  the  Laminae. 

The  ligaments  that  binds  the  laminae  together  consist  of 
yellow  ligamentous  fibres,  called  the  ligamenta  subjlava.  By 
their  upper  extremity  they  are  attached  to  the  anterior  surface 
of  the  lamina  above,  and  by  their  lower  extremity  they  are 
attached  to  the  posterior  surface  and  upper  border  of  the  one 
below.     This  is  necessitated  by  the  imbricated  arrangement  of 

Des  Anat— 8 


114  DESCRIPTIVE  ANATOMY. 

the  laminae.  They  are  thicker  iu  the  loins  than  in  the  back 
and  neck,  and  the  thickest  portion  corresponds  to  the  position 
of  the  spinous  process. 

Ligaments  of  the  Spinous  Processes. 

The  spinous  processes  are  connected  by  two  lig-ameuts,  the 
s lipjri  Rnd  intersf>inous.  'Vhe  sup7'aspi>io2is  is  a  round  cord, 
which  extends  from  the  seventh  cervical  vertebra  to  the  sacrum, 
attached  to  the  tips  of  the  spinous  processes.  This  cord  is  con- 
tinued upward  by  a  more  prominent  band,  which  has  received 
the  name  of  the  lig-cunentum  nuchae  (L.  nucha,  a  nape).  This, 
in  man,  is  composed  almost  entirely  of  fibrous  tissue,  and  is 
simply  a  division  of  the  supraspinous  lig^ament.  The  inter- 
s-pinous  lig-ament  consists  of  thin  fibres,  which  are  attached  to 
the  adjacent  edg-es  of  the  spinous  processes;  and  is  found  only 
in  the  dorsal  and  lumbar  regions. 

Ligaments  of  the  Transverse  Processes. 

Only  in  the  lower  dorsal  and  lumbar  regions  are  the  trans- 
verse processes  held  together  by  a  few  scattered  intermediate 
fibres,  called  intertransverse  ligaments,  extending  between  the 
adjacent  edges  of  the  corresponding  transverse  processes. 

The  Articulation  of  the  Head  with  the  Spine,  and  the  First 
with  the  Second  Cervical  Vertebra. 

The  Atlo-Axoid  Articulation. 

The  articulation  between  the  Atlas  and  the  axis  consists  of 
a  diarthrodial  and  arthrodial  joint  on  each  side,  formed  by  the 
articular  processes,  as  seen  between  other  vertebrse,  and  of  a 
pivot  joint,  in  front,  between  the  posterior  face  of  the  anterior 
arch  of  the  atlas  and  the  front  of  the  odontoid  process  of  the 
axis. 

The  anterior  atlo-axoid  ligament,  usually  described  as  two, 
consists  of  a  broad  band  of  ligamentus  fibres  attached  below 
to  the  front  of  the  body  of  the  axis  as  far  up  as  the  base  of  the 
odontoid  process,  and  above  to  the  lower  border,  anterior  sur- 
face and  tubercle  of  the  anterior  arch  of  the  atlas.  That  part 
occupying  the  middle  line  is  thicker  than  the  lateral  fibres  and 


LIGAMENTS.  115 

is  described  as  a  separate  lio-ament.  It  is  merely  a  continua- 
tion of  the  anterior  common  lig-ament  of  the  spine. 

The  posterior  atlo-axoid  li^^ament  is  a  membrane-like  fold 
closing"  in  the  space  between  the  vertebrse  behind.  It  is  attached 
above  to  the  posterior  surface  and  lower  border  of  the  posterior 
arch,  extending-  from  the  capsular  lig-ament  of  one  side  to  that 
of  the  other  and  blending-  with  the  capsules.  Below  it  seizes 
the  laminae  of  the  axis. 

The  transverse  ligament  is  a  strong-  band,  broader  in  the 
centre  than  at  either  extremity,  attached  firmly  by  either  end 
to  the  inner  face  of  the  lateral  mass  of  the  atlas,  stretching- 
across  the  odontoid  process  and  firmly  binding-  the  latter  to 
the  anterior  arch  of  the  atlas.  As  it  passes  over  the  odontoid 
process  a  vertical  band  of  fibres  crosses  it,  some  of  them  de- 
rived from  the  transverse  lig-ament,  to  be  attached  by  one  end 
to  the  base  of  the  odontoid  process  and  by  the  other  to  the 
basilar  process  of  the  occipital.  This  g-ives  the  lig-ament  the 
form  of  a  cross,  hence  its  name,  crucial  lig-ament. 

The  two  capsular  ligaments  are  attached  around  the  mar- 
gins of  the  articular  facets  on  the  two  vertebrae,  blending- 
with  the  posterior  atlo-axoid  lig-ament. 

There  are  four  synoval  sacs  connected  with  the  articulation. 
Two  belong-  to  the  joints  formed  by  the  articular  processes, 
one  is  interposed  between  the  front  of  the  ondontoid  process 
and  the  facet  on  the  anterior  arch  of  the  atlas,  while  one  inter- 
poses between  the  posterior  face  of  the  odontoid  process  and 
the  front  of  the  transverse  lig-ament. 

The  Occipito-Atloid  Articulation. 

This  is  a  movable  joint  of  the  condyloid  variety,  the  articu- 
lating- surfaces  being-  the  two  condyles  of  the  occipital  above 
and  the  superior  articular  facets  of  the  atlas  below.  The  lig-a- 
ments,  seven  in  number,  are 

Two  anterior  occipito-atloid  Posterior  occipito-atloid 

Two  Lateral  Occipito-Atloid  Two  capsular. 

The  central  part  of  the  anterior  occipito-atloid  ligament 
is  a  rounded  cord  attached  below  to  the  tubercle  on  the  ante- 


116  DESCRIPTIVE  ANATONY. 

rior  arch  of  the  atlas  and  above  to  the  under  face  of  the  basi- 
lar process  of  the  occipital.  It  is  the  upward  continuation  of 
the  anterior  atlo-axoid,  and  through  it  of  the  anterior  common 
ligament  of  the  spine.  The  lateral  portion  of  the  ligament  is 
a  broad  and  thin  band  attached  above  to  the  margin  of  the 
foramen  magnum  and  below  to  the  anterior  arch  of  the  atlas, 
extending  to  the  beginning  of  the  capsular  ligaments,  with 
which  it  blends. 

The  jyosterior  occipito-atloid  is  a  broad  and  thin  membra- 
nous band  attached  above  around  the  margins  of  the  foramen 
magnum  and  below  to  the  upper  border  and  posterior  surface 
of  the  posterior  arch  of  the  atlas.  It  corresponds  to  the  liga- 
ments between  the'laminae  in  the  vertebral  column,  but  contains 
no  elastic  fibres. 

The  capsular  ligaments  are  attached  around  the  margins  of 
the  condyles  above  and  the  receiving  surfaces  on  the  atlas  be- 
low. Behind  and  in  front  they  blend  with  the  anterior  and 
posterior  ligaments. 

The  two  lateral  ligaments  blend  with  the  sides  of  the  two 
capsular  ligaments  and  are  attached  below  to  the  transverse 
process  of  the  atlas,  extending  above  to  the  jugular  process  of 
the  occipital  bone. 

The  Occipito-Axoid  Ligaments. 

The  occipito-axoid  lig-anient  is  a  broad  membranous  band 
which  continues  the  posterior  common  ligament  of  the  spine 
upward  to  the  occipital.  It  is  attached  belov/  by  some  fibres 
to  the  body  of  the  third  cervical  vertebra  and  to  the  body  of 
the  axis.  Passing  upward  it  covers  over  the  odontoid  process 
and  the  crucial  ligament  and  is  attached  to  the  anterior  margin 
of  the  foramen  magnum,  passing  upon  the  basilar  process  to 
blend  with  the  dura. 

The  odontoid  or  check  liga?7ient  con'^i^i^  of  three  parts.  The 
lateral  portions  are  attached  below  to  the  pit  on  the  side  of  the 
odontoid  process  and  above  to  depressions  found  on  the  inner 
face  of  the  condyles.  The  central  portion  is  attached  below 
to  the  tip  of  the  odontoid  process  and  above  to  the  margin  of 
the  foramen  magnum. 


LIGAMENTS.  117 

The  vertebral  artery  supplies  both  of  these  articulations. 
The  loop  between  the  first  and  second  cervical  nerves  supplies 
the  articulation  between  the  axis  and  the  atlas,  while  the  sub- 
occipital supplies  the  occipito-atloid  articulation. 
Sacro- Vertebral  Articulation. 

The  joint  between  the  sacrum  and  last  lumbar  vertebra,  is 
similar  to  that  between  two  vertebrae,  the  articulating-  sur- 
faces being  the  articular  processes  of  the  two  bones.  The 
ligaments  are  the  same  as  between  any  two  vertebrae,  with  the 
addition  of  two  ligaments  on  each  side,  the  ilio-hunbar  and 
himbo-sacral,  which  are  generally  considered  among  the  liga- 
ments of  the  pelvis.  The  ilio-lumbar  extends  from  the  trans- 
verse process  of  the  fifth  lumbar  vertebra  outward  to  the 
ilium  just  above  and  in  front  of  the  ear-shaped  articular  sur- 
face. The  lumbo-sacral  passes  from  the  transverse  process 
of  the  fifth  lumbar  vertebra  downward  and  outward  to  the 
wing  of  the  sacrum. 

Movemoits.  Movement  between  the  occipital  and  the  atlas 
is  mainly  confined  to  the  backward  and  forward  movements, 
though  lateral  movement  is  permitted  to  some  extent.  In  the 
nodding  movements  of  the  head,  flexion  and  extension,  the 
condyles  of  the  occipital  glide  backward  and  forward  on  the 
articular  surfaces  of  the  atlas.  Thus,  in  flexion  the  chin  is 
carried  to  the  chest  while  the  condyles  pass  backward  in  their 
articular  cavities.  In  extension  the  head  is  carried  backward 
and  the  condyles  move  forward.  In  the  slight  lateral  move- 
ments the  head  is  carried  towards  the  shoulder  and  the  con- 
dyle of  that  side  passes  inward  while  the  one  of  the  opposite 
side  passes  outward  in  the  corresponding  cavity.  Motion  be- 
tween the  atlas  and  axis  is  confined  to  revolution  of  the  atlas 
around  the  odontoid  process  of  the  axis.  In  this  movement, 
the  head  is  turned  to  one  or  the  other  side  the  articular  facet 
gliding  toward  that  side  over  the  facet  on  the  process,  while 
the  inferior  facet  of  the  atlas  of  the  side  to  which  motion  is 
made,  glides  backward  on  the  axis  and  the  opposite  facet  glides 
forward. 

Moveynents  of  the  spine  as  a  whole.  The  amount  of  motion 
which   may  take  place  between  any  two  contiguous  vertebrae 


118  DESCRIPTIVE  ANATOMY. 

is  but  slight,  yet  the  column  as  a  whole  enjoys  a  wide  rang-e 
as  well  as  a  great  variety  of  movements.  These  movements 
are  the  four  ang-ular  movements,  flexion,  bending-  forward, 
extension,  bending*  backward,  and  rig-ht  and  left  lateral  move- 
ment. In  addition  to  these  a  considerable  amount  of  rotation, 
by  twisting"  of  the  lig-amentous  fibres  is  permitted.  In  flexion 
the  body  bends  forward,  compressing*  the  anterior  fibres  of 
the  intervertebral  disks  and  putting"  the  posterior  fibres  on 
the  stretch,  the  spine  becoming-  convex  backward.  This 
movement  is  limited  not  only  by  the  compressibility  of  the 
disks  but  by  the  tension  on  the  posterior  fibres,  while  the 
supra  and  interspinous  and  the  sub-flava  ligaments  are  all 
stretched.  The  superior  articular  processes  g-lide  upward  on 
the  inferior  in  this  movement.  Flexion  and  extension  are  both 
free  in  the  cervical  and  lumbar  regions,  the  vertical  direction 
of  the  articular  processes  limiting  the  movement  in  the  dorsal. 
Lateral  flexion  is  most  free  in  the  cervical  region,  the  inver- 
sion of  the  superior  articular  processes  limiting  it  in  the  lum- 
bar, while  the  attachment  of  the  ribs  prevents  it  in  the  dorsal, 
where  the  shape  and  direction  of  the  articular  processes  would 
indicate  that  it  should  be  most  free.  In  this  movement  the 
articular  process  of  the  side  away  from  which  motion  is  made 
glides  upward  on  the  one  below,  the  reverse  movement  taking 
place  on  the  side  flexed.  The  lateral  margins  of  the  disks 
would  be  compressed  and  the  fibres  of  all  ligaments  on  the 
opposite  side  put  on  the  stretch.  Rotation  of  the  column 
takes  place  by  twisting  the  fibres  of  the  intervertebral  disks. 
It  is  free  in  the  cervical  region,  slight  or  imperceptible  in  the 
dorsal  on  account  of  the  ribs,  while  the  large  size  of  the  supe- 
rior facets  as  compared  to  the  inferior  allows  some  rotation 
in  the  lumbar  region  in  spite  of  the  fitting  in  of  the  superior 
processes  between  the  inferior.  Of  course  in  rotation  there 
is  a  certain  amount  of  gliding  of  the  articular  processes,  the 
movement  being  arrested  by  the  stretching  of  the  vertical 
fibres  of  the  disks. 

The  Sterno-Clavicular  Articulation. 
This  is  a  movable  joint  of  the  saddle  shaped  variety,  or  a  joint 
by  reciprocal  reception.     It  is  formed   by  the  saddle  shaped 


LIGAMENTS.  119 

articular  surface  on  the  inner  extremity  of  the  clavicle,  which 
is  concave  from  above  downward  and  forward  and  convex 
from  above  downward  and  backward,  and  a  similar  surface 
on  the  upper  angle  of  the  manubrium,  aided  b}''  a  concavity 
on  the  cartilaufe  of  the  first  rib.  The  following-  ligaments 
bind  the  bones  together  : 

Capsular  Romboid,  or  Costo-Clavicular 

Interclavicular  Inter-articular  fibro-cartilage. 

The  inter-articular  fihro-cartilag-c  is  attached  by  one  end  to 
the  upper,  posterior  part  of  the  inner  end  of  the  clavicle  and 
by  the  other  to  the  junction  of  the  cartilage  of  the  first  rib 
with  the  articular  depression  on  the  lateral  aspect  of  the  manu- 
brium. It  serves  the  double  purpose  of  holding  the  bones 
together  and  at  the  same  time  divides  the  joint  into  two  syno- 
vial cavities. 

The  ca-psnlar  lig-ameiit  is  a  thick  band  of  fibres  completely 
surrounding  the  tjoint  but  thicker  at  some  points  than  at 
others.  Thus  it  is  seen  to  be  much  more  thickened  behind  than 
elsewhere,  being  sometimes  described  as  the  posterior  liga- 
ment of  the  joint.  In  front  it  blends  with  the  tendon  of  the 
sterno-mastoid  muscle,  above  with  the  interclavicular  ligament 
while  below  it  is  continuous  with  the  Romboid.  The  deepest 
fibres  of  this  ligament  pass  from  the  two  bones  to  the  interar- 
ticular  cartilage,  and  not  from  bone  to  bone,  while  the  more 
superficial  fibres  pass  from  the  margin  of  the  receiving  cavity 
on  the  manubrium  and  cartilage  on  the  first  rib  to  the  margfin 
of  the  articular  surface  on  the  clavicle. 

The  interclavicular  linanieut  is  a  strong  thick  band  attached 
to  the  upp_'r  an  1  posterior  aspect  of  the  clavicle  of  one  side, 
blending  with  the  fibres  of  the  capsule,  then  passes  into  the 
interclavicular  notch  to  be  attached  to  the  posterior  part  of 
the  upper  border  of  the  manubrium,  and  rises  to  be  attached 
to  the  inner  back  part  of  the  opposite  clavicle. 

The  roniljoid^  or  cosio-clavicular  ligament  is  a  set  of  short 
fibres  resembling  fibro  cartilage  which  extend  from  the  rom- 
boid impression  of  the  clavicle  downward,  forward  and  inward 
to  be  attached  to  the  upper  face  of  the  cartilage  of  the  first  rib. 


120  DESCRIPTIVE  ANATOMY. 

There  are  two  synovial  membranes,  one  interposed  between 
the  cartilag-e  and  the  manubrium  and  the  other  between  the 
inner  extremity  of  the  clavicle  and  the  cartilag-e.  In  some  cases 
the  cartilag-e  is  worn  throug-h  and  the  synovial  sacs  communi- 
cate with  each  other,  practically  forming-  one  sac. 

The  blood  supply  is  mainly  from  a  branch  of  the  Internal 
Mammary.  The  nerve  supply  is  from  the  branch  to  the  sub- 
clavius. 

The  movements  of  the  joint,  which  take  place  in  all  direc- 
tions, are  confined  within  a  narrow  rang-e  and  are  always  of 
a  g-liding-  character.  The  cartilage  accompanies  the  clavicle  in 
all  of  its  movements  except  upward.  Thus  in  movement  of 
the  shoulder  backward,  the  inner  end  of  the  clavicle,  with  the 
interarticular  cartilag-e,  passes  forward;  in  forward  movement 
of  the  shoulder,  the  clavicle  passes  backward;  in  upward  move- 
ment of  the  shoulder  the  clavicle  passes  downward;  but  in 
downward  movement  of  the  shoulder,  the  clavicle  passes  up- 
ward, putting-  the  fibres  of  the  cartilag-e  on  the  stretch  and 
limiting-  the  extent  of  the  movement. 

Scapulo-Ciavicular  Articulation. 

This  is  a  movable  joint  of  the  arthrodial  variety.  The  ar- 
ticulating- surfaces  are  an  oval  facet  on  the  outer  extremity  of 
the  clavicle  and  a  corresponding-  facet  on  the  anterior  edg-e  of 
the  acromion  process  of  the  scapula.  It  must  be  observed  that 
the  clavicle,  in  its  outward  course,  passes  just  above  the  cora^ 
coid  process  of  the  scapula,  and,  while  it  does  not  articulate 
with  it,  receives  a  lig-ament  from  it. 

The  bones  are  held  tog-ether  by  two  sets  of  lig-aments,  a 
capsular,  surrounding-  the  articular  surfaces,  and  acoraco-clavi- 
cular  binding-  the  clavicle  to  the  coracoid  process. 

The  caf>sular  ligament  is  a  strong-  but  lax  band  of  fibres 
surrounding-  the  joint  and  attached  to  the  clavicle  beyond  the 
articular  facet.  Inferiorly  these  fibres  pass  as  far  as  the 
coraco  clavicular  lig-ament  with  which  they  blend.  Above, 
they  are  streng-thened   by   fibres  of  the  deltoid  and  trapezius. 

The  coraco-clavicular  consists  of  two  portions,  the  conoid 
and  the  trapezoid.     The  conoid  lig-ament  is  triang-ular  in  form 


LIGAMENTS.  121 

and  is  attached  by  its  apex  to  the  coracoid  process  close  to  the 
supra-scapular  notch,  while  its  base  is  inserted  into  the  conoid 
tubercle  and  posterior  border  of  the  clavicle.  The  trapezoid, 
blended  internally  with  the  conoid,  has  its  surface  looking- for- 
ward and  backward.  Below  it  is  attached  to  a  rido-e  on  the 
upper  aspect  of  the  coracoid  process,  while  above  it  is  attached 
to  the  oblique  ridg-e  running- forward  and  outward  from  the 
conoid  tubercle  to  the  anterior  border  of  the  clavicle. 

This  joint  has  an  interarticular  fibro  cartilag-e,  which,  how- 
ever, is  often  absent.  When  this  is  present  there  are  two 
S3'novial  sacs,  otherwise,  but  one. 

The  -joint  is  supplied  by  the  acromial  thoracic  and  supra- 
scapular arteries  and  by  the  circumflex  and  suprascapular 
nerves. 

The  movenioits  of  the  joint  are  confined  to  a  slight  g-liding- 
of  the  articular  surfaces  upDn  one  another.  Usually  the 
scapula  is  the  bone  which  moves;  but,  of  course,  when  the 
scapula  is  fixed,  the  clavicle  may  gflide  upward,  downw^ard 
backward  or  forward. 

Ligaments  of  the  Scapula. 

Stretched  between  different  points  on  the  scapula  are  two 
ligaments,  coraco-acromial  and  transverse.  The  coraco-acro- 
viial,  thick  and  triang-ular,  is  attached  by  its  apex  to  the  tip  of 
the  acromion  and  by  its  base  to  the  coracoid  process,  serving- 
as  a  protecting-  arch  for  the  shoulder  joint.  The  transverse 
ligament  passes  over  the  supra-scapular  notch,  from  one  ex- 
tremity to  the  other,  converting^  it  into  a  foramen. 

The  Shoulder  Joint. 

The  shoulder  is  a  joint  of  the  diarthrodial  class  and  enar- 
throdial  or  ball  and  socket  variety.  The  bones  entering-  into  its 
formation  are  the  upper  extremity  of  the  humerus,  with  its 
g-lobular  head,  anatomical  neck  and  two  tuberosities  ;  and  the 
g-lenoid  cavity  of  the  scapula,  supported  b}'  its  neck  and  over- 
hung- by  the  c(;racoid  and  acromion  processes.  The  lig-aments 
of  the  joint  are  properly  but  two,  the  g-lenoid  and  capsular, 
thoug-h  some  accessory  bands  of  the  latter  are  frequently  dig-- 


122  DESCRIPTIVE  ANATOMY. 

nified  as  separate  ligaments.  The  g-lenoid  lio-ament  is  a  band 
of  fibro  cartilag-e,  triangular  on  cross  section,  which  is 
attached  by  its  base  around  the  margin  of  the  glenoid  cavity 
and  serves  to  deepen,  but  more  especially  to  widen  this  cavity. 
It  is  connected  above  with  the  head  of  the  biceps  muscle  which 
passes  through  the  joint,  and  by  its  margin  is  attached  to  the 
capsular  ligameat. 

The  caps2ilar  lig-ctment  is  a  strong  but  loose  sac  completely 
investing  the  articulation  but  not  holding  the  bones  in  apposi- 
tion with  each  other.  It  is  simply  a  bag  of  which  the  upper 
end  is  closed  by  the  glenoid  cavity  and  the  lower  by  the  artic- 
ular surface  of  the  humerus.  Above,  this  ligament  is  attached 
around  the  margin  of  the  glenoid  cavity,  extending  on  the 
neck  of  the  scapula  further  above  than  below  and  blending 
with  the  glenoid  ligament.  Below,  it  is  attached  around  the 
anatomical  neck  of  the  humerus  but  is  prolonged  over  the 
tuberosities,  between  which  it  is  continuous  with  the  trans- 
verse band  which  binds  the  tendon  of  the  biceps  in  its  groove. 
Inferiorly  it  is  prolonged  over  the  surgical  neck  of  the  humer- 
us to  a  slight  extent.  The  upper  part  is  very  much  thicker 
than  any  other  portion  of  the  ligament.  One  portion,  that 
extending  from  the  base  of  the  coracoid  process  to  the  greater 
tuberosity  of  the  humerus  is  the  portion  individualized  as  the 
coraco-humeral  ligament.  In  the  interior  of  the  joint  there 
may  sometimes  be  seen  a  fold  in  the  synovial  membrane  called 
the  gleno-humeral  ligament.  The  capsule  is  nearly  surroun- 
ded by  muscles  whose  tendons, as  they  pass  over  it,are  blended 
with  the  ligament  and  supply  the  greater  part  of  its  strength. 

The  synovial  meinhrane  is  extensive.  It  lines  the  interior 
of  the  capsule  and  is  reflected  over  the  margins  of  the  articular 
surfaces,  but  does  not  reach  the  p.jints  of  greatest  pressure. 
A  prolongation  of  the  membrane  is  continued  over  the  tendon 
of  the  biceps  muscle  and  the  sac  usually  communicates  with  a 
bursa  beneath  the  subscapularis  muscle  and  frequently  with 
one  beneath  the  infraspinatus. 

The  joint  is  powerfully  reinforced  and  protected  not  only 
by  the  numerous  muscles  which  surround  it  but  also  by  a  pro- 
tecting arch  formed  by  the  acromion  and  coracoid  processes  and 


LIGAMENTS.  123 

the  coraco-acromial  lig-ament  stretched  between  them.  The 
muscles  are,  above  the  supra  spinatus,  postero-superiorly  the 
infraspinatus  and  teres  minor,  antero-internally  the  subscapu- 
laris  :  while  above,  behind,  to  the  outer  side  and  in  front  the 
fibers  of  the  deltoid  form  a  cushion  over  the  joint.  The  first 
four  muscles  blend,  at  their  insertion,  with  the  capsule. 

The  arterial  supply  is  chiefly  from  the  anterior  and  posterior 
circumflex,  but  branches  are  derived  from  the  dorsalis  scapula? 
and  suprascapular  arteries.  The  nerves  are  the  suprascapular 
and  circumflex. 

Movements  and  mechanism.  The  leng-th  of  the  capsular 
lig"ament,  the  shallowness  of  the  receiving*  cavity  and  the  com- 
paratively larg-e  size  of  the  humeral  head,  permit  this  joint  to 
enjoy  a  gfreater  variety  and  extent  of  movement  than  au}^ 
other  in  the  body.  Like  all  enarthrodial  joints  it  is  capable 
of  the  four  ang-ular  movements,  their  combination,  circum- 
duction, and  axial  rotation.  In  flexion  the  humerus  with 
the  forearm  is  carried  forward,  the  head  of  the  bone 
spinning-  in  the  articular  cavity  around  an  axis  which  is 
drawn  from  the  centre  of  the  head  throug-h  the  centre  of 
the  g"reater  tuberosity,  to  the  centre  of  the  g"lenoid  cavity.  In 
extension  the  reverse  movement  takes  place,  with  of  course  a 
reversal  of  the  mechanism.  In  abduction  the  humerus  is 
carried  away  from  the  mid-line  of  the  body,  the  hand  raised 
toward  the  shoulder,  while  the  head  of  the  humerus  g-lides 
downward  in  the  g-lenoid  cavity  until  it  presses  on  the  inferior 
fibres  of  the  capsular  lig-ament.  When  the  humerus  is  carried 
in  abduction  to  arig-ht  angle  with  the  body,  further  movement 
is  arrested  by  the  impact  of  the  bone  against  the  arch  of  the 
acromion,  further  movement  in  this  direction  being-  effected  by 
the  g-liding-  of  the  scapula  on  the  thoracic  wall.  Adduction  is 
the  reverse  of  abduction.  Adduction  is  limited  by  the  elbow 
coming-  in  contact  with  the  side  and  cannot  be  carried  further 
without  first  flexing-  the  arm.  Circumduction  is  the  combina- 
tion of  these  movements,  the  head  of  the  humerus  assuming 
the  position  of  flexion,  abduction,  extension  and  adduction,  the 
arm  and  forearm  describing-  a  cone  whose  apex  is  at  the 
shoulder  joint.     In  rotation   the  head  of  the    humerus   moves 


124  DESCRIPTIVE  ANATOMY. 

around  an  axis  drawn  from  the  centre  of  the  head  downward 
throug-h  the  internal  condyle,  the  head  moving-  backward  in 
inward  and  forward  in  outward  rotation. 

The  relation  of  the  long-  head  of  the  biceps  to  this  joint  is  so 
peculiar  as  to  demand  special  mention.  Attached  to  the  upper 
marg-in  of  the  gflenoid  cavity,  where  it  is  blended  with  the 
g-lenoid  lig-ament,  it  passes  across  the  upper  outer  aspect  of 
the  joint,  pierces  its  capsular  lig-ament  and  is  covered  by  a 
prolong-ation  of  the  synovial  membrane  which  lines  the  cavity. 
This  tendon,  therefore,  becomes  a  powerful  ag-ent  in  retaining- 
the  head  of  the  humerus  in  apposition  with  the  g-leniod  cavity 
and  thus  strengthens  the  joint  on  its  upper  and  outer  aspect. 

Radio-Ulnar  Articulation. 

The  articulation  between  the  two  bones  of  the  forearm  forms 
a  diarthrodial  joint  of  the  trochoid  or  pivot  variety.  The 
bones  articulate  at  both  the  upper  and  lower  extremity,  being- 
separated  by  the  interosseous  space  throughout  the  shafts. 

The  lig-aments  holding-  the  bones  tog-ether  are  found  at  their 
npp^r  and  lower  extremities  and  between  their  shafts.  Above, 
the  two  bones  are  held  together  by  one  ligament,  the  orbicular 
which  forms  three-fourths  of  a  ring-,  the  other  fourth  being 
the  lesser  sigmoid  cavity  of  the  ulna.  The  ligament  surrounds 
the  articular  rim  of  the  radius  and  is  attached  by  its  two  ends 
to  the  extremities  of  the  lesser  sigmoid  cavity.  The  lower 
fibres  are  tightly  stretched  around  the  radius  just  below  the 
head,  rendering  it  very  difficult  to  release  that  bone  from  its 
grasp. 

The  shafts  are  connected  b}^  two  ligaments,  the  interosseous 
and  the  oblique.  The  oblique  is  a  narrow  band  which  passes 
downward  and  outward  from  the  ulna,  at  the  base  of  the  coro- 
noid  process,  to  the  radius  just  below  the  tuberosity.  It  is 
often  wanting. 

The  interosseous  membrane  extends  from  the  lower  extrem- 
ities of  the  bones  upward  about  two-thirds  the  length  of  the 
shafts,  leaving  an  interval, above  which  is  the  oblique  ligament. 
Its  fibres  are  directed  downward  and  inward  between  the  inner 
border  of  the  radius  and  the  outer  border  of  the  ulna.     About 


LIGAMENTS.  125 

the  lower  third  of  the  forearm,  the  membrane  is  pierced  by  a 
foramen  for  the  anterior  interosseous  artery. 

At  their  lower  extremities  the  bones  are  held  togfether  by 
two  lig-aments  and  the  trtanfj;-ular  fibro-cartilag-e.  The  two 
lig^aments  are  an  anterior  and  a  posterior  passing- across  the  two 
bones.  The  triangfular  cartilag-e  tips  the  summit  of  the  capi- 
tulum  ulnae;  and  excludes  it  from  the  wrist  joint.  Bv  its  apex 
it  is  attached  to  the  pit  between  the  styloid  processof  the  ulna 
and  the  capitulum  ulnae;  by  its  base  to  the  narrow  roug-h  sur- 
face separating-  the  carpal  and  sigmoid   cavities  of  the  radius. 

The  movements  are  two,  and  in  both  the  radius  alone  moves. 
It  can  move  forward,  pronation,  or  backward,  supination,  and 
in  both  the  hand  is  carried  with  it.  In  these  movements  of 
rotation,  or  revolution,  the  radius  rotates  around  an  axis  repre- 
sented by  an  imaginary  line  drawn  from  the  centre  of  the  head 
of  the  radius  throug-h  the  centre  of  the  capitulum  ulnae;  conse- 
quently in  performing-  pronation  the  sig-moid  cavity  of  the  radius 
moves  forward  on  the  articular  rim  of  the  capitulum  ulnae,  the 
reverse  occurring-  in  supination,  while  the  head  of  the  radius 
rotates  in   the  lesser   sigmoid  cavity  and   orbicular   lig-ament. 

The  Elbow. 

This  is  a  diarthrodial  joint  of  the  g-iug-lymoid  variet3\  The 
bones  entering-  into  its  formation  are  the  trochlear  surface  and 
the  rounded  eminentia  capatata  on  the  lower  extremity,  of  the 
humerus,  and  the  g-reater  sig-moid  cavity  of  the  ulna  with  the  cup- 
shaped  upper  extremity  of  the  radius.  The  shape  of  the  articu- 
lar surfaces  furnished  by  the  radius  and  humerus  would 
render  this  joint  one  of  the  enarthrodial  variety  ;  but  the 
movements  are  so  restricted  by  the  close  lig-amentous  union 
^-between  the  ulna  and  radius,  that  the  joint  presents  but  one 
of  the  peculiar  movements  of  the  enarthrodial  joints — rotation. 

The  lig-aments  are  anterior  and  posterior,  internal  and 
external  lateral.  There,  as  always,  some  thin  fibres  which 
connect  the  various  parts  of  the  lig-amentous  bands  tog-ether, 
completing-  the  capsule  around  the  joint. 

The  anlerior  lig-aDieiit  is  attached  above  to  the  humerus  just 
above  the  coranoid  fossa,  while  below  it  seizes  the  lower  sur- 
face of  the  coranoid  process  and  the  orbicular  ligament. 


126  DESCRIPTIVE  ANATOMY. 

^\\Q,  f)Osterior  lig-aments  is  attached  above  to  the  humerus 
just  above  the  olecranon  fossa  and  below  to  the  g-roove  on  the 
upper  surface  of  the  olecranon,  and  to  the  bone  immediately 
behind  this.     It  is  much  thinner  and  weaker  than  the  anterior. 

The  external  lateral  ligament  is  attached  above  to  a  depres- 
sion beneath  the  external  condyle  while  its  base  is  attached  to 
the  orbicular  lig-ament. 

The  internal  lateral  is  attached  above  to  the  internal  con- 
dyle while  below  it  expands  into  two  fasciculi  with  a  triang-ular 
interval,  filled  with  thin  fibres,  between  them.  The  most 
anterior,  which  may  be  traced  to  its  attachment  to  the  front  of 
the  internal  condyle,  is  attached  below  to  the  margin  of  the 
great  sigmoid  cavity  on  the  coronoid  process.  The  posterior, 
attached  above  to  the  back  of  the  internal  condyle,  is  below 
attached  to  that  margin  of  the  sigmoid  cavity  furnished  by  the 
olecranon  process.  By  means  of  a  few  thin,  scattered  fibres, 
the  lateral  ligaments  are  connected  with  the  anterior  and  pos- 
terior ligaments,  thus  completing  an  imperfect  capsule. 

The  synovial  membrane  is  extensive.  It  lines  the  whole  of 
the  inner  face  of  the  capsule,  extending  upward  behind  to  the 
olecranon  and  in  front  to  the  coranoid  fossa  ;  while  below  it 
covers  the  interior  of  the  orbicular  ligament  and  furnishes  the 
lining  for  the  articulation  at  the  superior  radio  ulnar  articula- 
tion. 

The  muscles  which  strengthen  the  joint  are  in  front  the 
brachialis  anticus,  behind  the  triceps  and  anconeus,  externally 
the  muscles  arising  from  the  external  condyle,  notably  the 
supinator  brevis  ;  and  internally  those  which  arise  from  the 
internal  condyle. 

The  move7Jients  are  flexion  and  extension,  to  which  should 
be  added  the  rotation  of  the  radius  when  that  bone  revolves  in 
the  lesser  sigmoid  cavity.  In  flexion  the  greater  sigmoid  cavity 
and  the  cup-shaped  articular  surface  of  the  radius  glide  upward 
on  the  corresponding  articular  surface  of  the  humerus,  the 
movement  being  arrested  when  the  coranoid  process  impinges 
upon  the  coronoid  fossa.  In  extension  the  reverse  would  occur 
and  the  movement  would  be  arrested  by  the  impact  of  the  beak 


LIGAMENTS.  127 

of  the  olecranon  on  the  bottom  of  the  olecranon  fossa.  The 
movement  of  the  radius  will  be  described  with  the  radio-ulnar 
articulation. 

The  arterial  supply  of  this  joint  is  derived  from  communi- 
catinof  branches  between  the  anastoraotica  mag-na,  the  superior 
profunda  and  inferior  profunda  arteries,  the  anterior,  posterior, 
and  interosseous  recurrent  branches  of  the  ulna,  and  from  the 
radial  recurrent.  The  nerve  supply  is  derived  from  the  ulna 
as  it  passes  between  the  internal  condyle  and  the  olecranon, 
the  median  is  said  to  furnish  two  filaments  while  the  musculo- 
cutaneous contributes  one  filament. 

The  Wrist  Joint. 

This  is  a  diarthrodial  joint  of  the  condyloid  variety.  The 
receiving-  cavity,  oval,  transversely,  concave  both  from  before 
backward  and  from  side  to  side,  is  furnished  by  the  lower  ex- 
tremity of  the  radius,  aided  by  the  triang-ular  cartilag-e  which 
shuts  out  the  ulna  from  participation  in  the  joint.  The  con- 
dyle is  provided  by  three  of  the  bones  of  the  first  row  of  the 
carpus,  scaphoid,  semilunar  and  cuneiform.  The  ligaments 
anterior,  posterior  and  two  lateral. 

All  lig-aments  of  this  joint  blend  with  the  ligaments  of  the 
carpus  and  can  with  difficulty  be  separated  from  them.  Thus 
the  anlcrior  ligament  is  attached  above  to  the  margin  of  the 
carpal  cavity  of  the  radius  and  to  the  anterior  radio-ulnar  liga- 
ment, and  to  the  anterior  margin  of  the  lower  end  of  the 
Ulna,  while  below  it  is  attached  to  the  bones  of  the  first  row 
of  the  carpus,  blending  with  the  anterior  palmer  ligamentous 
fibres  which  bind  together  the  first  and  second  rows.  The 
fiosterior  is,  in  like  manner,  attached  above  to  the  posterior 
margin  of  the  carpal  cavity  and  to  the  posterior  radio-ulna 
ligament  and  below  to  the  back  of  the  bones  forming  the  first 
row  of  the  carpus,  blending  with  the  dorsal  carpal  ligaments 
binding  the  two  rows  together.  The  external  lateral  lig-amcnt 
is  attached  above  to  the  styloid  process  of  the  radius  and  be- 
low to  the  tuberosity  of  the  scaphoid  and  to  the  trapezium. 
The  internal  lateral  liij;-ament  is  attached  above  to  the  styloid 
process  of  the  ulna,  below  to  the  inner  side  of  the  cuneiform 
and  unciform,  to  the  latter  through  the  medium  of  the  internal 


128  DESCRIPTIVE  ANATOMY. 

lateral  ligament  of  the  carpus.     Between  these  bands  are  fibres 
which  convert  this  lig-ament  into  a  capsule. 

The  synovial  membrane  lines  the  interior  of  the  ligament- 
ous fibres  and  to  a  slight  extent  dips  ia  between  the  scaphoid 
and  semilunar  and  between  the  semilunar  and  cuneiform. 
There  are  no  muscles  which  directly  strengthen  the  joint. 
Many  tendons  pass  over  it  but  their  laxity  prevents  their  add- 
ing strength  except  in  certain  positions  of  the  joint.  Thus  in 
flexion,  with  the  closed  fist,  the  extensor  tendons  strengthen 
it  behind,  and  in  extension,  with  the  hand  open,  some  strength 
is  given  by  the  flexors.  The  tendons,  also,  by  the  tonic  con- 
traction of  the  muscles,  aid  in  retaining  the  bones  in  apposi- 
tion. 

The  movements  are  those  usual  in  condyloid  articulations, 
flexion,  extension,  abduction,  adduction  and  circumduction. 
The  mechanism  will  be  readily  understood  if  it  is  borne  in 
mind  that  in  all  movements  of  condyloid  joints  the  distal  ex- 
tremity moves  in  a  direction  opposite  to  that  of  the  condyle. 
Thus  in  flexion,  the  hand  passes  forward  on  the  forearm  while 
the  condyle  moves  backward  in  its  receiving  cavity,  pressing 
against  the  posterior  fibres  of  the  ligament.  E)xagger%ted 
movement  as  from  a  fall  on  the  flexed  hand,  would  produce 
dislocation.  In  .extension  the  mechanism  is  the  reverse  of 
flexion.  In  adduction  the  hand  is  carried  toward  the  mid  line 
of  body  while  the  condyle  passes  outward,  the  movement  be- 
ing limited  by  the  external  lateral  ligament.  In  abduction  the 
reverse  is  true.  The  combination  of  these  movements  make^^ 
circumduction,  which  may  be  either  inward  or  outward.  In 
the  latter  the  hand  would  pass  from  flexion  to  abduction, 
thence  to  extension,  then  to  adduction  and  again  to  flexion. 
The  condyle  passing  first  backward,  then  inward,  forward, 
outward  and  so  to  backward  again. 

The  wrist  joint  gets  its  arterial  supply  from   the  anterior 
and  posterior  carpal  arches  of  the  radial  and  ulna.     The  inter- 
osseous arteries,  anterior  and  posterior,  as  well  as  some  of  the     / 
ascending  branches  of  the  deep  palmar  arch  also  contributing  / 
to  its  supply. 

The  ulna  and  posterior  interosseous  furnish  the  nerve  supply. 


LIGAMENTS.  129 

Articulation  of  Carpus  and  Metacarpus. 

The  bones  of  the  carpus,  which  lie  in  the  same  row,  are  held 
tog-ether  by  ligfamentous  fibres  passing"  across  them  in  front 
and  behind,  palmar  and  dorsal  ligaments,  and  by  fibres  which 
seize  the  adjoining-  surface  of  opposing-  bones,  called  interosse- 
ous ligaments.  Between  the  trapezium  and  trapezoid  there  is 
no  interosseous  ligament.  In  the  same  manner  the  metacarpal 
bones  of  the  four  fing-ers  are  held  tog-ether  at  their  bases.  The 
two  rows  of  carpal  bones  are  held  tog-ether  by  lig-amentous 
fibres  passing  from  one  to  the  other  in  front  and  behind,  pal- 
mar and  dorsal  lig-aments,  and  by  two  lateral  lig-aments,  the 
external  passing-  from  the  scaphoid  to  the  trapezium,  the  inter- 
nal from  the  cuneiform  to  the  unciform. 

The  metacarpal  bones  of  the  four  fing-ers  are  held  to  the 
second  row  of  carpal  bones  by  fibres  in  front  and  behind,  pal- 
mar and  dorsal  lig-aments,  and  in  one  situation  by  interosseous 
fibres  extending  from  the  adjacent  parts  of  the  os  mag-numand 
unciform  to  the  bases  of  the  third  and  fourth  metacarpal  bones. 

The  synovial  membrane  between  the  first  and  second  rows 
sends  prolong-ations  upward  and  downward  between  the  indi- 
vidual bones  of  the  two  rows,  as  well  as  between  the  proximal 
extremities  of  the  metacarpal  bones  into  the  carpo- metacarpal 
articulations.  This  is  not  true  of  the  synovial  sac  between  the 
metacarpal  bone  of  the  thumb  and  the  trapezium. 

The  Trapezio-Metacarpal  Joint. 

This  articulation  belongs  to  the  movable  class  and  saddle- 
shaped  variety.  It  is  invested  by  a  capsular  ligament,  and 
allows  the  four  angular  movements  and  their  combination^ 
circumduction. 

The  Metacarpo-Phalangeal  Articulation. 

The  knuckle  joint,  or  metacarpo-phalang-eal,  is  of  the  mova- 
ble class  and  condyloid  variety.  The  condyle  is  furnished  by 
the  head  of  the  metacarpal  bone  and  the  receiving-  cavity  by 
the  top  of  the  corresponrling-  phalanx,  aided  by  a  plate  of  carti- 
lag-e  known  as  the  anterior  lig-ament  of  the  joint. 

Des  Anat— 9 


130  DESCRIPTIVE  ANATONY. 

The  lig-aments  are  tzvo  latercil^  seizing-  both  bones  on  their 
lateral  aspect  just  beyond  the  articular  surface.  The  place  of 
a  posterior  llg-ament  is  supplied  by  the  extensor  tendons  of  the 
finger.  The  anterior  is  not  a  lig-ament  in  the  true  sense  of  the 
word,  being  only  amassof  fibro-cartilaginous  material  attached 
to  the  front  edg-e  of  the  articulating-  surface  on  the  base  of  the 
phalanx,  and  increasing  the  receiving*  cavity. 

To  this  lig-ament  is  attached  a  band  of  transverse  fibres 
which  stretch  between  the  distal  ends  of  the  metacarpal  bones 
and  bind  them  to  one  another. 

Inter-Phalangeal  Articulations. 

These  joints  are  of  the  diarthrodial  class  and  the  hing-e  variety, 
the  trochlear  surface  being  presented  by  the  head  of  one  pha- 
lanx and  the  receiving-  surface  bv  the  base  of  the  other. 

The  lig-aments,  anterior  and  tvjo  laterrl,  are  attached  like 
those  of  the  metacarpo-phalang-eal  articulations,  the  extensor 
tendons  here,  also,  taking-  the  place  of  posterior  lig-aments. 

The  carpal  articulations  are  supplied  by  the  carpal  arches 
and  the  deep  palmar  arches.  The  nerves  are  derived  from 
the  ulnar,  median  and  posterior  interosseous.  The  fingers  are 
supplied  by  their  respective  dig-ital  branches  both  for  nerves 
and  arteries.  The  movements  of  the  carpal  joints  are  confined 
to  a  slig-ht  gliding-  of  one  bone  on  the  other, — the  same  state- 
ment applying-  to  the  carpo-metacarpal  joint,  except  the  thumb. 
Movement  at  the  metacarpo-phalangeal  joint  consists  of  the 
four  ang-ular  movements  and  their  combination,  circumduction. 
Movement  is  freer  at  the  index  and  little  fing-ers  than  at  the 
other  two.  Movement  at  the  inter-phalangeal  articulation  is 
confined  to  flexion  and  extension. 

Temporo-Maxillary  Articulation. 

This  articulation  is  formed  by  the  condyle  of  the  lower  jaw 
and  the  g-lenoid  cavity  of  the  temporal  bone. 

This  is  a  diarthrodial  joint  of  the  condyloid  variety,  and 
presents  four  lig-aments,   viz  :  internal  and   external  lateral, 
capsular  and  stylo-maxillary  and  an  inter-articular   fibro-car-^ 
tilage,  which  is  sometimes  perforated  ;   when  this  is  the  case, 


LIGAMENTS.  131 

there  is  but  one  synovial  sac,  otherwise  there  are  two,  one  be- 
tween the  cartilage  and  the  condyle  and  the  other  between 
the  cartilao^e  and  the  g-lenoid  cavity. 

The  external  lateral  lig-ameut  is  attached  to  the  zyg^oraa 
above,  from  its  tubercle  forward,  and,  passing-  downward  and 
backward,  is  attached,  below,  to  the  outer  border  of  the  neck 
of  the  condyle. 

The  internal  lateral  liaament  is  a  specialized  piece  of  the 
deep  cervical  fascia,  attached  above  to  the  spine  of  the  sphe- 
noid and  below  to  the  shelf  of  bone  forminor-  the  lower  margin 
of  the  inferior  dental  foramen. 

The  capsular  ligament  consists  of  fibres  of  varying  thick- 
ness, attached  above  around  the  articular  margin  of  the  glen- 
oid cavity  and  below  to  the  neck  of  the  condyle  of  the  lower 
jaw.  This  ligament  is  slightly  thickened  at  its  inner  part, 
while  the  external  lateral  ligament  is  merely  a  thickening  of 
the  capsule.  The  capsule  is  attached  throughout  its  circum- 
ference to  the  edge  of  the  interarticular  cartilage. 

The  intcr-ariicular fibro-cartilage  is  oval  in  outline,  thinner 
at  the  centre  than  at  the  circumference,  concavo-convex  on  its 
upper  and  concave  on  its  lower  surface.  Its  margin  is  closely 
attached  to  the  capsular  ligament. 

The  stylo-maxillary  is,  properly,  not  a  ligament  of  this 
joint.  It  extends  from  the  styloid  process  of  the  temporal 
bone  to  the  angle  and  posterior  border  of  the  ramus  of  the 
lower  jaw. 

The  lower  jaw  receives  its  nervous  supply  from  the  auri- 
culo- temporal  branch  of  the  inferior  maxillary.  The  arterial 
supply  is  from  the  temporal. 

The  joint  is  strengthened  on  the  outer  side  by  the  masseter, 
internally  by  the  internal  pterygoid  and  above  by  the  tempo- 
ral. 

The  movements  are  elevation  and  depression,  lateral  and 
forward  movement.  In  depression  the  jaw  recedes  from  the 
upper  and  the  condyle,  when  the  movement  is  not  extreme, 
rolls  on  the  inter-articular  cartilage  around  an  axis  drawn 
through   its  own   centre.     When,  however,  the    movement  is 


132  DESCRIPTIVE  ANATOMY. 

carried  farther,  both  condyle  and  cartilag-e  roll  forward  on 
the  eminentia  articularis,  exag-g-erated  movement  leading-  to 
dislocation. 

Elevation  is  the  reverse  of  depression. 

In  lateral  movement  the  jaw  is  twisted  to  one  or  the  other 
side,  the  condyle  moving"  backward  in  the  g-lenoid  cavity  on 
the  side  toward  which  motion  is  made. 

In  forward  movement  the  two  condyles  are  drag-g-ed  forward 
on  the  eminentia  articularis,  the  lower  jaw  being  protruded 
beyond  the  upper. 

Costo-Sternal  Articulation. 

The  ribs  have  attached  to  their  anterior  extremities  the  cos- 
tal cartilag-es,  which  prolong-  the  seven  true  ribs  to  the  side  of 
the  sternum,  where  the  cartilagfes  are  received  into  the  pits 
found  there  and  are  held  in  place  by  lig-amentous  fibres  passing- 
from  them  to  the  sternum  in  front  and  behind.  The  cartilag-es 
of  the  second  and   third  ribs  have  also  each  an  inter-articular 

lig-ament. 

The  Articulations  of  the  Pelvis. 

The  articulations  of  the  pelvis  are  four,  viz  :  that  between  the 
fifth  lumbar  vertebra  and  the  sacrum,  that  between  the  sacrum 
and  coccyx,  that  between  the  sacrum  and  the  os  innominatum 
of  each  side  and  that  between  the  two  ossa  innominata. 

Sacro-Vertebral  Articulation. 

The  joint  between  the  sacrum  and  last  lumbar  vertebra,  is 
similar  to  that  between  two  vertebrae^  the  articulating-  surfaces 
being-  the  articular  processes  of  the  two  bones.  The  ligaments 
are  the  same  as  between  any  two  vertebrae,  ^vith  the  addition 
two  ligaments  on  each  side,  the  ilio-lumhar  and  lumbosacral, 
which  are  generally  considered  among  the  ligaments  of  the 
pelvis.  The  ilio-lumbar  extends  from  the  transverse  process 
of  the  fifth  lumbar  vertebra  outward  to  the  ilium  just  above 
and  in  front  of  the  ear-shaped  articular  surface.  The  lumbo- 
sacral passes  from  the  transverse  process  of  the  fifth  lumbar 
vertebra  downward  and  outward  to  the  wing-  of  the  sacrum. 


LIGAMENTS.  133 

The  Sar?'o- Coccygeal  lig-aments  are  an  intervertebral  disk, 
small  and  insignificant,  and  an  anterior,  posterior  and  lateral 
lig-aments  passing-  directly  from  one  bone  to  the  other. 

The  Sacro-Iliac  articulation,  symphysis  or  synchondrosis, 
is  formed  bv  the  auricular  facets  found  on  the  sacrum  and 
ilium,  each  of  which  is  coated,  in  the  recent  state,  by  a  thin 
plate  of  cartilaofe.  The  lig^aments  of  the  joint  are  an  anterior 
and  a  posterior  and  the  two  sacro-sciatic,  g^reater  and   lesser. 

The  anterior  sacro-iliac  ligament  is  a  thin  plane  of  fibres 
passing-  from  the  front  of  the  sacrum  to  the  inner  face  of  the 
ilium. 

The  posterior  sacro-iliac  lig-ament  is  a  dense  and  thick  mass 
of  fibres,  both  oblique  and  horizontal,  passing-  between  the 
contig-uous  surfaces  of  the  two  bones  and  filling*  in  the  deep 
depression  which  exists  between  them.  The  fibres  are 
attached  to  the  roug-h  surface  on  the  ilium  behind  the  auricu- 
lar facet  and  to  the  similar  depression  on  the  lateral  aspect  of 
the  sacrum  as  well  as  to  the  posterior   face  of  the  latter  bone. 

The  g-reater  sacro-sciatic  ligament  is  attached  by  its  poste- 
rior extremity  to  the  posterior  inferior  spinous  process  of  the 
ilium,  and  to  the  side  and  posterior  face  of  the  sacrum  and 
coccyx.  Passing-  forward  it  runs  below  the  spine  of  the  isch- 
ium and  is  attached  to  the  tuberosity  of  the  ischium,  its  inner 
edg-e  being-  free  and  curved  upward  upon  itself. 

The  lesser  sacro-sciatic  ligament  is  blended  with  part  of 
the  g-reater  at  its  posterior  extremity,  being-  attached  to  the 
side  of  the  sacrum  and  coccyx,  slig-htly  in  front  of  the  greater, 
and  not  extending-  so  hig-h  up  as  the  former.  In  front  it  is 
attached  to  the  spine  of  the  ischium. 

The  lesser  sacro-sciatic  ligament  forms  the  lower  boundary 
of  the  g-reater  sacro-sciatic  foramen;  while  that  part  of  the 
g-reater  sacro-sciatic  which  extends  from  the  point  where  the 
two  lig-aments  separate  to  the  tuberosity  of  the  ischium,  forms 
the  lower  boundary  of  the  lesser  sacro-sciatic  foramen. 

The  Symphysis  Pubis. 

The  articulation  between  the  ossa  innominata  is  formed 
between  the  two  pubic  bones,  and  is  known  as  the  symphysis 


134  DESCRIPTIVE  ANATOMY. 

pubis.  Kach  bone  presents  an  oval  articular  surface,  whose 
long-  diameter  is  downward  and  backward,  coated  by  a  thin 
plate  of  encrusting-  cartilag-e.  The  two  plates  are  in  contact 
only  at  the  back  part,  leaving-,  in  front,  a  wedg-e-shaped  space 
filled  by  fibres  passing-  between  the  two  plates.  Besides  this 
interarticular  lig-ament,  there  are  four  others — superior,  con- 
sisting-of  fibres  passing- between  the  two  bones  above;  inferior, 
fibres  passing-  between  the  two  bones  below,  and  filling-  in  the 
interval  between  the  two  rami,  so  as  to  form  a  smoothly- 
curved  arch;  anterior,  fibres  passing-  between  the  bones  in 
front,  and  posterior  consisting-  of  similar  fibres  behind. 

The  articulations  are  supplied  by  branches  from  the  lateral 
sacral,  ilio-lumbar,  middle  sacral  and  internal   pudic  arteries. 

The  nerves  are  received  from  the  cords  of  the  sacral  plexus. 

The  Hip  Joint. 

The  Hi j)  Joint  is  one  of  the  ball  and  socket  articulations,  of 
course,  belong-ing-  to  the  euarthrodial,  or  movable  variety. 
The  bones  which  ent^r-fdto  its  formation  are  the  three-quarter- 
sphere  articular  surface  found  on  the  upper  extremity  of  the 
femur  to  correspond  to  the  Acetabulum,  a  receiving-  cavity 
found  at  the  junction  of  the  three  bones,  the  Ilium,  the  Ischium 
and  the  Pubes,  which  compose  the  os  innoniinatum.  This 
cavity  is  articular  throug-hout  its  entire  extent.  There  is  a 
lower,  inner  portion,  at  the  bottom  of  the  cavit}^  a  non-articu- 
lar roug-hened  surface,  which  in  the  articulated  skeleton  serves 
partly  to  form  the  attachment  of  the  lig-ament  w^hich  lies  in  the 
interior  of  the  joint,  and  partly  serves  for  the  lodg-ment  of  the 
mass  of  fat,  which  prevents  jarring-  of  the  joint,  and  at  the 
same  time  lodg-es  the  blood  vessels  which  supply  the  joint  and 
prevents  pressure  upon  these  vessels. 

The  Ligaments  which  hold  the  bones  tog-ether  are  the 
Capsular  lig-ament,  which  surrounds  the  joint;  the  Cotyloid, 
which  surrotlnds  the  marg-in  of  the  cavity,  and  serves  to 
deepen  it  ;  the  Transverse,  which  crosses  the  cotyloid  notch  ; 
and  in,  the  interior  of  the  articulation,  there  is  a  round 
cord  which  is  known  as  the  Lig-amentum  Teres.  Some  anato- 
mists add  other  ligaments,  which  are  unimportant   when  con- 


LIGAMENTS.  135 

sidered  as  separate  lio*aments,  being-  merely  portions  of  t 
capsular  lig-ament  which  are  developed  by  the  strain  upon  the 
joint.  One  of  these,  the  Ilio  femoral  lig-ament,  extends  from 
just  behind  the  anterior  inferior  spinous  process  of  the  ilium 
across  to  a  point  close  to  the  Trochanter  mijor  of  the  femur, 
one  of  the  points  at  which  the  strain  is  very  great.  Another, 
called  the  Ischio-femoral,  extends  from  the  tuberosity  of  the 
ischium  ;  while  a  third,  somewhat  less  important  than  the 
others,  extends  from  near  the  femoral  line  of  the  os  pubes,  and 
is  known  as  the  Pectineal,  or  Pubo-femoral  lig-ament.  These 
lig-aments  are  not  deserving-  of  a  separate  name.  The  proper 
description  is  to  say  that  the  capsular  lig-ament  is  streng-thened 
at  the  superior  and  inferior  extremities  of  the  joint  by  fibres 
which  come  respectivel}'^  from  the  spinous  process  of  the  ilium, 
from  the  ischium,  and  from  the  os  pubes. 

The  Capsular  Lig-am2)it,  thick  and  powerful,  is  attached 
above  to  the  brim  of  the  Acetabulum.  As  it  passes  around 
downward  and  backward,  it  will  be  noticed  that  the  lig-ament 
extends  further  forward  on  the  Acetabulum;  that  is,  the  extent 
of  its  attachment  increases  as  we  pass  around  to  the  posterior 
aspect  of  the  joint.  On  reaching-  the  lower  portion  of  the  joint, 
this  lig-ament  is  found  to  occupy  all  the  space  above  the  g-roove 
on  the  ischium.  On  reaching-  the  upper,  inner  portion  of  the 
joint  it  expands  considerably^  nearly  to  the  ilio-pectineal  line. 
As  the  li(jfa.ment  passes  downward  it  completely  envelops  the 
joint;  and  its  attachment  is  ag-ain  irreg-ular  when  the  attach- 
ment to  the  femur  is  reached.  Superiorly  it  extends  to  what 
is  known  as  the  superior  cervical  txibercle,  which  is  found  pro- 
jecting-from  the  upper  front  part  of  the  neck  at  its  junction  with 
the  trochanter  major;  superiorly  to  this,  it  extends  behind  a 
part  of  the  Trochanter  major;  then  follows  the  spiral  line, 
and  winds  around  until  it  passes  just  in  front  of  the  Tro- 
chanter minor;  then  extends  until  it  passes  upward  and  just 
misses  the  dig-ital  pit,  and  reaches  the  starting--point. 

One  of  the  most  important  of  the  lig-amentary  bands  com- 
posing- the  Capsular  lig-ament  is  the  so-called  ""T Lig-ament,''^ 
which  may  be  seen  better  in  the  dry  specimen  than  in  the 
recent.     The   two   branches   rise  by   the  "tail"  or  "stem"  of 


136  DESCRIPTIVE  ANATOMY. 

the  Y  from  just  below  and  just  behind  the  anterior  inferior 
spinous  process  of  the  ilium;  and  as  they  pass  downward, 
though  there  is  never  any  actual  Interval  between  them,  the 
central  fibres  are  very  thin,  and  the  fibres  above  and  below, 
particularly  above,  are  very  thick,  hence  the  resemblance  to  a 
Y.  The  superior  fibres  of  the  Y  lig-ament  are  attached  to  the 
superior  cervical  tubercle:  the  inferior  fibres  are  inserted  into 
the  spiral  line  just  as  they   reach  the  inner  aspect  of  the  bone. 

The  others  are  of  comparatively  little  importance. 

The  Ilio-^ectineal  lig-ament  is  a  long-  slender  baud  of  fibres, 
which  starts  nearly  at  the  pectineal  line  of  the  pubes  ;  and 
passes  down  to  reach  the  spine,  a  little  lower.  The  band 
which  comes  from  the  tuberosity  of  the  ischium  arises  just 
below  the  g-roove  ;  and  then  stretches  across,  to  be  inserted 
near  the  digital  pit  close  to  the  Trochanter  major.  These 
ligamentous  bands  are  of  comparatively  little  importance. 

The  Cotyloid  cavity  is  deepened  by  a  ring  of  fibro-cartilage, 
which  is  described  as  being  nearly  a  complete  circle,  but  fails 
to  extend  all  the  way  around  the  joint ;  that  is,  it  is  said  to  be 
horse-shoe  shaped,  the  direction  of  the  bend  in  the  horse-shoe 
being  downward  and  inward  at  the  cotyloid  notch.  What  is 
in  reality  a  continuous  ligament,  extending  all  the  way  around 
the  joint,  anatomists  have  preferred  to  describe  as  two  liga- 
ments, differentiating  between  the  Cotyloid  lig-amejit  and  the 
Transverse  ligament^  which  passes  across  the  cotyloid  notch, 
becoming  continuous  at  its  extremities  with  the  cotyloid  liga- 
ment, although  the  two  have  the  same  histiological  structure. 
However,  in  accordance  with  general  usage  they  are  to  be 
described  as  two  separate  ligaments.  The  Cotyloid  lig-ame7it 
is  described  as  being  triangular  upon  cross  section,  although 
it  is  not  quite  so,  the  outer  face  being  distinctly  convex,  the 
inner  upon  the  cross  section  proving  to  be  not  a  straight  line, 
but  a  curved  line,  thus  forming  the  concavity  which  is  neces- 
sary to  receive  the  convex  head  of  the  femur.  The  thin  edge 
projects  away  from  the  bone  ;  the  thick  edge  is  attached  to 
the  margin  of  the  cavity  all  the  way  around. 

As  above  described,  the  Cotyloid  ligament  upon  reaching 


LIGAMENTS.  137 

the  cotyloid  notch,  changes  its  name,  and  becomes  the  Trans- 
verse lig-ament,  which  is  therefore  merely  a  continuation  of 
the  Cotyloid. 

The  Lig-amentiim  Teres  is  a  band  of  lig-ameutous  fibres, 
holding-  the  bones  which  form  the  joint  in  position.  It  is  at- 
tached to  the  margin  of  the  depression  in  the  bottom  of  the 
cavity;  its  lower  fibres  are  firmly  attached  to  the  transverse 
ligament;  and  at  its  lower  extremity  it  passes  into  the  depres- 
sion on  the  head  of  the  femur. 

In  this,  as  in  all  other  movable  joints,  there  is  a  synovial 
membrane,  w^hich  here  presents  one  peculiarity.  Though  the 
Ligamentum  Teres  has  been  spoken  of  as  a  ligament,  it  is  not 
a  liofament  in  the  true  sense  of  the  word.  As  a  rule  the 
synovial  membranes  disappear  as  they  approach  the  region  of 
pressure  in  a  bone  ;  but  the  Ligamentum  Teres  can  be  dis- 
tinctly demonstrated  as  a  synovial  membrane  at  the  points  of 
greatest  pressure.  The  synovial  membrane  starts  at  the  pit 
on  the  head  of  the  femur  ;  and  passes  downward,  covering  all 
of  the  head  of  the  femur.  Leaving  the  bone  itself,  it  appears 
on  the  capsular  ligament ;  continues  on  the  cotyloid  face  until 
it  reaches  the  cotyloid  cavity  ;  then  sweeps  across  the  mass  of 
fat  lying  in  this  cavity  ;  and  then  passes  all  around  the  Liga- 
mentum Teres.  The  Ligamentum  Teres,  therefore,  does 
not  enter  into  the  joint  at  all,  and  unless  the  synovial 
membrane  is  first  cut,  neither  the  Ligamentum  Teres,  nor 
the  mass  of  fat  which  lies  in  the  bottom  of  the  depression 
have  any  communication  with  the  joint. 

The  Movements  of  which  the  hip  joint  is  capable  are,  of 
course,  all  of  the  movements  of  the  enarthroidal  joint;  viz., 
flexion,  extension,  adduction,  abduction,  circumduction,  and 
rotation.  Any  two  or  more  of  these  movements  which  are  not 
antagonistic  with  each  other  may,  of  course,  be  combined  ;  for 
instance,  there  may  be  flexion  of  the  thigh  upon  the  pelvis  at 
the  same  time  with  adduction,  abduction,  or  axial  rotation. 

Flexion,  or  the  movement  of  the  thigh  forward,  is  the  most 
extensive  of  the  movements  of  the  joint.  In  the  prepared 
specimen  flexion  may  be  continued  until  there  is  almost  a  com- 


138  DESCRIPTIVE  ANATOMY. 

plete  revolution  of  the  joint.  The  movement  consists  simply 
of  spinning-  the  head  in  tHe  cavity.  There  is  no  chang-e  of 
position  with  reference  to  the  ball  in  the  socket,  the  ball  simply 
turning-  in  the  socket  on  an  axis  drawn  through  the  Trochanter 
major  from  the  centre  of  the  head  of  the  femur.  Complete 
flexion  is  checked  by  the  powerful  band  of  fibres  forming  the 
upper  limb  of  the  Y  ligament,  though  of  course  in  the  living- 
man  the  movement  is  stopped  long-  before  this  by  the  contact 
between  the  thick  muscles  of  the  abdomen  and  the  muscles 
of  the  thig-h. 

Extension,  the  movement  of  the  thig-h  backward,  is  much 
less  free  than  flexion.  The  movement  is  hindered  by  the 
Pectlno-femoral  band  in  the  dead  subject ;  and  is  also  limited, 
in  the  living-  man,  by  the  mass  of  muscles  passing  in  front  and 
behind. 

In  Abduction  and  Adduction  there  are  complete  changes 
without  rotation.  In  Abduction,  which  is  a  movement  of  the 
thig-h  away  from  the  mid-line  of  the  body,  as  the  limb  is  carried 
outward,  the  head  of  the  femur  passes  downward  to  the  bottom 
of  the  acetabular  cavity,  so  that  it  can  be  felt  throug-h  the 
lig-amentous  fibres.  If  the  movement  is  carried  to  excess  in 
the  living-  man,  splitting-  of  the  fibres  takes  place. 

Adduction  is  more  limited  in  this  than  in  almost  any  other 
joint  in  the  body.  If  the  body  be  in  the  anatomical  position, 
of  course  the  movement  is  arrested  by  the  limb  on  the  other 
side;  if  taken  in  a  position  of  semi-flexion,  adduction  can 
never  be  equal  to  abduction,  because  it  is  checked  by  the  pow- 
erful superior  fibres  of  the  capsular  lig-ament. 

Circuinduction  is  a  combination  of  all  the  preceeding-  move- 
ments. In  this  movement  the  limb  pisses  from  flexion  to 
abduction,  from  abduction  to  extension,  from  extension  to  ad- 
duction, from  adduction  back  to  flexion. 

Axial  Rotation  is  usually  described  as  the  rotation  on  the 
line  which  is  drawn  from  the  centre  of  the  head  of  the  femur 
to  the  internal  tuberosity  of  the  femur.  The  line  is  more 
nearly  through  the  centre  of  the  lower  extremity  of  the  femur. 


LIGAMENTS.  139 

The  muscles  which  strengfthen  the  joint  are  as  follows: 

Above,  the  rectus  and  g-luteus  minimus.  In  front,  the  psoas 
magnus  and  iliacus  internus.  Internally,  the  pectineus  and 
obturator  internus.  Behind,  the  outward  rotators  of  the  thig-h, 
obturators,  internus  and  externus,  pyriformis,  the  g-emelli 
and  the  quadratus  femoris.  Or,  beg-inning-  at  random  and 
naming-  them  in  the  order  in  which  they  lie  around  the  joint, 
we  have,  g-luteus  minimus,  rectus,  iliacus  internus,  psoas 
mag-nus,  pectineus,  obturator  externus,  quaratus  femoris, 
g-emellus  inferior,  obturator  internus,  g-emellus  superior  and 
pyriformis. 

The  arteries  supplying-  the  joint  are  derived  from  the  obtu- 
rator, sciatic,  internal  circumflex  and  g-luteal. 

The  nerve  supply  for  the  joint  is  draw^n  from  articular 
branches  from  the  sacral  plexus,  g-reat  sciatic,  obturator, 
and  a  filament  from  the  branch  of  anterior  crural  supplying- 
the  rectus  muscle. 

The  Knee  Joint. 

This  is  the  largest  and  for  many  reasons  the  most  important 
joint  in  the  body.  By  the  formation  of  the  bones  it  is  the 
weakest  joint  in  the  body,  its  strength  consisting  entirely  in 
the  powerful  bands  of  ligamentous  fibres  and  the  muscles 
by  which  it  is  reinforced.  It  is  usually  classed  as  a  "hinge 
joint",  being  the  analogue  of  the  elbow;  but  it  is  really  no  more 
of  a  hinge  than  the  elbow  is  a  pure  hinge.  In  formation  it  is 
very  complex,  being  a  double  condyloid  joint,  combined  with 
a  trochlea,  and  possessing  three  articulations.  Its  articulations 
may  be  extended  to  four,  as  some  of  the  cartilages  which  enter 
into  the  formition  of  the  joint  are  so  arranged  as  to  establish 
an  articulation  between  themselves  and  the  bones  to  which  they 
are  attached.  The  condyles  and  their  receiving  cavities  per- 
mit all  of  the  movements  belonging  to  the  usual  condyloid 
articulations.  The  mistake  of  calling  the  knee  a  hinge  joint 
arises  from  the  fact  that  the  classification  of  joints  is  based  on 
the  movements  of  which  the  joints  are  capible  and  not  on  the 
shape  of  the  bones  which  enter  into  their  formation. 

The  Bones  which  compose  the  knee  joint  are  the  two  condyles 
of  the  femur,  the  two  glenoid  cavities  on  the  upper  extremity 


140  DESCRIPTIVE  ANATOMY. 

of  the  tibia,  and  the  posterior  surface  of  the  patella.  The 
lig-aments  which  bind  the  bones  together  are  divided  into  two 
sets:  the  external,  or  exterior  lig-aments,  and  the  interior 
lig-aments. 

The  Exterior  Ligaments  consist  of  an  anterior,  a  posterior, 
an  external  lateral,  and  an  internal  lateral. 

The  Anterior  Lig-cunent,  or  Liganientam  Patellar,  the  most 
powerful  of  all  the  bands  of  lig-amentous  fibres  attached  to  the 
joint,  is  nothing-  more  than  the  tendon  of  the  E)xtensor  triceps 
cruris.  This  muscle  passes  downward  until  it  reaches  the 
upper  border  of  the  patella.  There  the  fibres  become  tendin- 
ous, and  spread  out  to  embrace  the  pitella,  passing-  all  around 
it,  some  being-  attached  to  its  upper  border,  others  extending- 
so  as  to  run  down  upon  its  lateral  borders,  while  others  run 
upon  its  anterior  surface,  the  posterior  surface  being-  left  free. 

This  tendon  passes  downward  until  it  reaches  the  lower 
portion  of  the  anterior  tubercle,  where  it  is  inserted,  leaving- 
a  little  space  between  itself  and  the  upper  portion  of   the  tibia, 

As  the  lig-amentum  patellje  descends  towards  its  insertion, 
it  does  not  diminish  in  size;  but  it  g-ives  off  from  its  lateral 
aspect  tendinous  fibres,  sometimes  spoken  of  as  the  lateral 
patellar  lig-aments,  which  pass  around  until  they  reach  the 
joint;  in  other  words,  they  form  a  complete  capsule  for  the  knee 
joint.  This  can  be  stated  of  every  joint  which  carries  a  syno- 
vial membrane. 

The  Posterior  Lig-anie)it  of  the  joint,  one  of  the  most  peculiar 
in  the  body,  is  a  set  of  fibres  running-  in  different  directions. 
In  one  way  or  another  these  are  attached  above  the  condyles 
of  the  femur.  Some  are  attached  at  those  depressions  where 
the  Gastrocnemius  and  the  Plantaris  rise;  and  then  extend 
across  the  upper  marg-in  of  the  condyloid  notch.  The 
central  fibres  extend  further  up  on  the  shaft  of  the  bone;  but 
these  instead  of  running-  downward,  run  backward  and  out- 
ward. The  central  and  enlarg-ed  portion  of  the  attachment  of 
the  Semi-menbranus  muscle  is  inserted  into  the  front  of  the 
femur,  and  spreads  upward  and  backward,  consequently 
forming-  the  middle   portion  of  the  posterior  lig-ament  of  the 


LIGAMENTS.  141 

joint.  Where  the  central  fibres  come  in  touch  with  the  external 
head  of  the  Gastrocnemius  muscle,  they  blend  with  the  fibres 
of  that  muscle.  The  lower  fibres  of  the  ligament  are  attached 
to  the  posterior  surface  of  the  tibia. 

The  hiternal  Lateral  Lig-ament  is  attached  above  to  the 
inner  tuberosity  of  the  femur;  passes  downward  and  is  attached 
to  the  internal  tuberosity  of  the  tibia;  but  the  fibres  continue 
down  to  the  internal  face  of  the  tibia. 

The  External  Lateral  Ligament  consists  of  two  bundles  of 
fibres;  and  is  described  by  some  as  having-  the  same  attachment 
below  and  a  different  attachment  above.  It  is,  properly  speak- 
ing, all  one  ligament.  Some  anatomists  assert  that  the  muscle 
which  passes  over  the  joint  constitutes  the  greater  portion  of 
the  ligament,  while  others  say  that  it  does  not  enter  into  it  at 
all.  The  origin  of  the  Popliteus  muscle  and  the  origin  of  the 
long  external  lateral  ligament  of  the  knee  joint  are  precisely 
the  same  thing.  They  are  attached  to  the  little  groove  on  the 
outer  surface  of  the  outer  tuberosity  of  the  femur.  From  that 
point  the  external  lateral  ligament  descends  to  become  attached 
to  the  styloid  process  of  the  fibula. 

The  remainder  of  it  is  nothing  further  than  the  tendon  of 
origin  of  the  Popliteus  muscle. 

The  interior  of  the  Joint  consists  of  a  set  of  fibres,  which 
are  not  ligaments,  but  are  cartilages,  without  any  function  in 
binding  the  bones  together.  They  serve  mainly  to  deepen  the 
cavit}',  but  are  very  peculiar  in  their  arrangement,  and  have  an 
entirely  different  function  to  perform.  There  is  a  synovial 
memVjrane  between  the  cartilages  and  the  tibia ;  and  it  is 
between  the  semilunar  cartilages  and  the  upper  extremity  of 
the  tibia  that  the  fourth  articulation,  mentioned  above  as 
belonging  to  the  knee  joint,  takes  place.  In  the  interior  of  the 
joint  there  are  a  pair  of  ligaments,  or  cartilages,  the  Semi-lu- 
nar cartilages;  running  across  at  the  anterior  aspect  of  the  joint 
from  one  cartilage  to  the  other  is  a  small  band  forming  a 
Tranverse  ligament;  binding  these  cartilages  down  to  the 
bone  are  a  set  of  very  short  fibres,  known  as  the  Coronary 
Ligarnenl ;  then,   in   the  interior  of   the    joint,    are  seen   two 


142  DESCRIPTIVE  ANATOMY. 

strong-  cords  which  cross  each  other  somewhat  in  the  form  of 
the  letter  X,  one  called  the  Anterior,  or  External,  Crucial 
Lig-avient,  the  other  the  Posterior,  or  Internal,  Crncial  Lig-a- 
ment.  In  addition  we  have  the  folds  of  synovial  membrane, 
one  called  the  Lig-amenticni  Mucosum,  and  the  other  the  Liga- 
ment a  Alaria. 

The  attachment  of  the  Senii-hinar  cartilages  is  one  of  the 
most  important  thing^s,  both  anatomically  and  surg-ically,  in  con- 
nection with  the  knee  joint.  ^]\q.  Externarv$>  nearly  circular, 
being-  but  slig-htly  oval  in  its  outline;  the  Internal,  on  the  con- 
trary, is  distinctly  oval,  being"  long-er  from  before  backward  than 
from  side  to  side.  The  external  is  attached  just  in  front  of 
the  spine  of  the  tibia;  and,  in  the  prepared  specimen,  is  attached 
just  between  the  spine  and  the  anterior  crucial  lig-ament,  blend- 
ing- with  the  anterior  crucial.  Behind,  it  is  attached  between 
the  crucial  lig-ament  and  the  internal  cartilag-e,  so  that  it  blends 
at  both  extremities  with  the  crucial  ligaments.  The  internal 
semi-lunar  cartilage,  which  is  much  long-er  than  the  external, 
passes  around  so  as  to  be  attached  in  front  of  the  anterior 
crucial  lig-ament.  It  does  not  blend  with  that  lig-ament  at 
all ;  and,  behind,  the  internal  cartilag-e  is  not  attached  to 
the  crucial  lig-ament.  The  cartilag-e  can  be  raised  up  in  any 
direction,  but  is  attached  to  the  bone  by  the  fibres  of  the 
capsular  lig-ament  of  the  joint.  In  truth  it  is  not  really 
attached  to  the  bone,  except  just  in  front  and  just  behind  the 
anterior  spine  of  the  tibia.  On  the  contrary,  all  of  the  fibres 
which  enter  into  the  formation  of  the  lig-aments  of  this  joint, 
with  the  exception  of  those  composing-  the  Lig-amentum  patellae, 
become  attached  to  the  edg-es  of  the  semi-lunar  cartilag-es;  and 
from  those  edges  they  pass  down  as  short  fibres  to  seek  their 
insertion  in  the  tibia.  They  bind  the  cartilag-es  in  position, 
but  leave  them  so  as  to  be  movable. 

The  Anterior  Crucial  Ligament  takes  its  orig-in  from  a 
point  just  in  front  of  the  spine  of  the  tibia.  Prom  that  orig-in 
it  passes  upward,  outward,  and  backward;  and  is  inserted  into 
the  internal  face  of  the  external  condyle  of  the  femur. 

The  Posterior  Crucial  Ligament  arises  from  behind  the 
spine  of  the  tibia;  and  is  blended  with  the  posterior  extremity 


LIGAMENTS.  143 

of  the  external  semi-lunar  cartilag-e.  From  that  orig"in  the 
direction  of  its  fibres  is  upward,  forward  and  outward;  and 
consequently  the  two  crucial  lig"araents  cross  each  other  in  the 
joint.  When  they  come  in  contact  with  each  other,  the  poste- 
rior crucial  ligfament  g-ivesolf  a  slip  of  fibres  which  decussates 
with  the  anterior  crucial  lio-ament.  The  posterior  lig-anient 
then  passes  on  to  its  insertion  in  the  external  face  of  the  internal 
cond^de  of  the  femur. 

The   folds  of  the   Synovial  Membrane  are   mixed    with  fat. 

The  Ligamentum  Mucosiun  v^,  io\xn6i  attached  to  the  front 
of  the  inter-condyloid  notch;  and  passes  from  that  point,  lying- 
bet  ween  the  patella  and  the  inter-condyloid  notch  of  the  femur, 
down  to  become  attached  to  the  lower  extremity  of  the  patella. 

From  the  lateral  edg-es  of  the  ligamentum  mucosum  are 
sent  off  the  fring-e-like  folds  with  masses  of  fat,  spoken  of 
as  the  Lig-amenta  Alaria.  The  synovial  membrane  is  the 
largest  in  the  body,  and  extends  to  surrounding  struc- 
tures. The  membrane  passes  down  from  the  articular 
surface  of  the  femur;  and  reaches  the  lig^amentum  muco- 
sum, which  has  a  few  ligamentous  fibres.  It  then  ascends 
and  reaches  the  patella  on  the  posterior  surface  of  the 
anterior  lig-ament;  but  a  lateral  view  of  it  would  continue  its 
course  down  until  it  reached  the  upper  surface  of  the  tibia. 
It  is  a  continuous  sack.  The  lateral  subdivisions  pass 
downward;  and  leaving-  the  femur,  pass  upward  as  far  as  the 
articular  surface  extends  in  the  mid-line,  including  the  crucial 
ligaments.  Traced  forward  from  the  crucial  ligaments,  the  folds 
pass  over  the  upper  surface  of  the  tibia,  run  over  and  line  the 
semi-lunar  cartilages,  and  then  pass  between  the  cartilag-es 
and  the  tibia,  so  as  to  form  a  sack.  As  the  fold  passes  down- 
ward, the  crucial  ligaments  are  left  out  of  the  joint,  another 
proof  that  must  at  one  time  have  been  separate  and  distinct 
articulations.  While  the  synovial  membrane  is  all  one  continu- 
ous sack,  there  is  a  space  above  the  articular  surface  of  the 
femur,  which  covers  the  non-articular  surface,  extending*  to  the 
point  where  the  attachment  of  the  Gastrocnemius  commences. 
The  membrane  surrounds  and  embraces  the  crucial  lio-aments 


144  DESCRIPTIVE  ANATOMY. 

and  cuts  them  off  from  the  joint;  it  extends  down  over  the 
patella  and  the  Ligfamentum  patellae  ;  passes  over  the  tibia, 
and  in  addition  lies  between  the  semi-lunar  cartilag-es  and  the 
upper  surface  of  the  tibia,  forming- a  movable  surface  between 
the  two.  The  membrane  frequently  communicates  with  little 
bursae  which  are  found  around  this  joint. 

The  External  Cartilage,  just  before  it  reaches  its  attach- 
ment, extends  its  transverse  band  across  to  become  attached 
to  the  Internal  Cartilage,  thus  forming-  the  Transverse  lig-a- 
ment  of  the  joint. 

Between  the  Li§ amentum  patellcF  and  the  upper  surface  of 
the  tibia,  there  is  a  little  sack,  which  does  not  communicate 
with  the  joint,  but  forms  a  bursa,  so  as  to  have  a  freely  g-liding- 
tendon  over  the  upper  extremity  of  the  tibia.  At  the  back  of 
the  joint,  beneath  the  two  heads  of  the  Gastrocnemius  muscle, 
are  found  two  more  burs^.  Beneath  the  tendon  on  the  inner 
side  is  found  another  ;  and  on  the  outer  side,  beneath  the  ten- 
don of  the  Popliteus,  is  found  another.  Any  one  of  these  may, 
and  frequently  do,  communicate  with  the  joint ;  hence  they 
are  known  as  the  Synovial  Bursce.  Between  the  skin  and  the 
front  of  the  patella  is  another  bursa,  which  can  be  easily 
found  in  the  healthy  man  and  which  does  not  communicate  with 
the  joint.     It  is  a  mucous  bursa. 

Actions.  This  joint  never  makes  the  movement  of  a  pure 
"hinge  joint."  If  placed  in  a  position  of  extreme  flexion,  the 
posterior  portion  of  the  condyles  rests  upon  the  posterior  part 
of  the  semi-lunar  cartilag-es.  Place  the  knee  in  a  position  of 
half-flexion,  and  the  central  portion  of  the  cartilag-e  then  rests 
upon  the  central  portion  of  the  c'ondyle,  the  axis  of  rotation 
having-  chang-ed  so  that  the  tibia  has  been  carried  forward 
about  half  an  inch.  Bring  the  leg"  further  forward,  and  the 
axis  of  rotation  will  have  been  brought  further  forward. 
When  the  joint  is  drawn  into  a  position  of  extreme  fl.exion,  the 
toe  is  bent  only  slig-htly  forward  ;  when  we  pass  from  extreme 
flexion  to  extreme  extension  there  is  an  inward  rotation,  which 
bring-s  the  toe  out  until  is  nearly  in  a  straig-ht  line.  That  is, 
there  is,  in  addition   to  the  rotation  of  flexion,  an   axial  rota- 


LIGAMENTS.  145 

tion,  except  for  the  fact  that  it  takes  place  on  two  points 
instead  of  one.  In  addition  to  the  movement  between  the 
femur  and  the  tibia,  there  is,  therefore,  an  actual  rotation  be- 
tween the  semi-lunar  cartilag-es  and  the  tibia.  Besides  these, 
there  is  an  incomplete  rotation,  a  movement  between  the  carti- 
lag-es and  the  femur  ;  and  at  the  same  place  a  constant  move- 
ment of  the  patella  on  the  femur.  When  the  limb  is  in 
extreme  flexion,  only  the  lower  portion  of  the  patella  is  in 
contact  with  the  femur  ;  when  drawn  up,  the  central  or  bulg-ed 
portion,  is  in  contact  with  the  femur  ;  and  in  extreme  exten- 
sion, the  upper  portion  is  in  contact  with  the  femur.  There 
is  a  line  extending-  from  the  centre  of  the  patella  vertically  and 
another  transversely ;  and  some  say  there  is  a  third  line, 
which  completes  the  division  of  the  patella  into  six  separate 
compartments. 

The  Muscles  which  strengthen  the  articulation  are,  prima- 
rily, the  Triceps  extensor  cruris  ;  behind,  the  two  heads  of 
the  Gastrocnemius  and  the  Plantaris  ;  on  the  outer  side,  the 
tendon  of  the  Biceps  flexor  cruris ;  and  on  the  inner  side,  the 
Semi-tendinosus,  which  is  in  reality  the  only  one  that  strengthens 
the  joint  internally.  The  Popliteus  pow^erfully  streng-thens  the 
joint  upon  its  outer  side  ;  and  it  is  a  powerful  streng-thening- 
agfent  on  its  posterior  aspect. 

The  arterial  supply  of  the  joint  is  furnished  by  articular 
branches  from  the  popliteal,  by  the  anterior  and  posterior 
recurrent  branches  of  the  anterior  tibial,  by  the  anastomotica 
magna  branch  of  the  femoral  and  by  the  descending-  branches 
from  the  external  circumflex. 

The  nerve  supply  is  derived  from  the  external  and  internal 
popliteal,  the  obdurator  and  from  the  anterior  crural. 

The  Tibio-Fibular  Articulation. 

The  upper  and  lower  extremities  of  these  bones  are  held 
tog-ether  by  lig-amentous  fibres,  while  there  is  a  strong- interos- 
seous membrane  extended  between  their  shafts. 

The  superior  tibio- fibular  joint  is  of  the  arthrodial  variety 
and  the  bones  are  held  together  by  anterior  iva(S.  posterior  lig-a- 
mentous fibres,  passing-  directly  between  the  contiguous  sur- 

Des  Anat— 10 


146  DESCRIPTIVE  ANATOMY. 

faces  of  the  two  bones.  They  are  united  by  a  few  scattered 
fibres  to  protect  the  synovial  membrane,  forming-  an  imperfect 
capsule.  The  synovial  memhrane  sometimes  communicates 
with  the  knee  joint. 

The  inferior  tibio-Jibular  joint  is  an  articulation  of  the 
amphiarthrodial  class.  A  rough  surface  is  presented  by  each 
of  the  bones  for  the  reception  of  the  powerful  interosseous 
lig-ament  which  passes  between  them.  There  are  also  anterior 
and  posterior  fibres  passing-  from  one  bone  to  the  other,  form- 
ing the  anterior  and  posterior  inferior  tibio-fibular  ligaments. 
The  lower  part  of  each  bone  presents  a  small  smooth  surface, 
coated  with  cartilage  in  the  recent  state  whose  synovial  mem- 
brane communicates  with  the  ankle  joint. 

The  interosseous  vienibrane  is  composed  of  oblique  fibres 
directed  downward  and  outward  and  extending  from  just  be- 
low the  knee  to  within  a  short  distance  of  the  ankle.  These 
fibres  are  attached  to  the  interosseous  ridges  on  the  two  bones. 
Above  the  membrane  is  seen  an  oval  aperture  for  the  trans- 
mission of  the  anterior  tibial  vessels.  At  its  lower  portion  the 
membrane  is  perforated  for  the  passage  of  the  anterior  pero- 
neal artery. 

Movements.  A  slight  gliding  movement  only  is  permitted 
between  the  two  bones  above  while  below  there  is  practically 
no  movement,  the  little  permitted  being  confined  to  a  slight 
twisting  of  the  fibres  of  the  interosseous  ligament. 

The  Ankle  Joint. 

This/o/;?/  belongs  to  the  movable  class  and  hinge  or,  more 
correctly,  the  mortise  and  tenon  variety.  Its  articular  surfaces 
are  contributed  by  the  lower  extremities  of  the  tibia  and 
fibula,  above,  and  the  upper  surface  of  the  astragalus  below. 

The  ligaments  consist  of  anterior,  posterior  and  two  lateral. 

The  anterior,  thin  and  fatty,  is  attached  above  to  the  front 
of  the  tibia  just  above  its  articular  surface  and  below  to  the 
upper  surface  of  the  neck  of  the  astragalus. 

Tho.  posterior,  more  insignificant  than  the  anterior,  is  mainly 
for  the  protection  of  the  synovial  membrane.  It  consists  of  a 
few  scattered  fibres  attached  above  to  the  tibia  and  below  to 
the  OS  calcis. 


IvIGAMEXTS.  147 

The  internal  lateral  or  deltoid  lig-ament,  is  a  dense  and 
powerful  mass  of  fibres  which  embraces  the  tip  of  the 
internal  malleolus  by  its  apex  and  by  its  broad  base  is 
attached  to  the  tuberosity  of  the  scaphoid,  to  the  inner  face  of 
the  astrag-alus,  below  the  articular  facet,  and  to  the  os  calcis, 
where  it  also  serves  to  bind  the  astragalus  and  the  os  calcis  to- 
gether.  On  section  this  ligament  is  seen  to  consist  of  two  layers. 

The  external  lateral  ligament,  usually  described  as  one,  is 
really  three  separate  ligaments.  The  anterior  fasciculus,  the 
weakest,  is  attached  above  to  the  anterior  border  of  the  exter- 
nal malleolus  and  passing  downward  and  forward  reaches  the 
upper,  outer  aspect  of  the  astragalus.  The  middle,  passes  from 
the  tip  of  the  malleolus  vertically  downward  to  the  tubercle  on 
the  outer  face  of  the  os  calcis.  The  posterior  is  attached  ex- 
ternally to  a  deep  depression  on  the  inner  face  of  the  malleolus 
and  passes  horizontally  inward  to  seize  the  outer  face  of  the 
astragalus  behind  its  articular  facet. 

The  synovial  membrane  is  extensive  and  lines  the  inner  face 
of  the  ligaments  as  well  as  the  bones. 

The  joint  is  strengthened  behind  by  the  tendo  Achilles, 
which  takes  the  place  of  a  posterior  ligament.  Antero-inter- 
nally  is  the  tibialis  anticus,  postero-internally  the  tibialis  pos- 
ticus while  externally  are  the  two  peroneal  tendons.  The 
flexor  and  extensor  tendons  are  too  lax  to  add  any  strength  to 
the  joint. 

The  malleolar  arteries  supply  the  joint  with  blood  while 
the  anterior  and  posterior  tibials  give  it  its  nervous  supply. 

The  movements  are  flexion  and  extension,  although  in  one 
position  a  slight  degree  of  lateral  movement  is  permitted.  In 
flexion  the  foot  is  drawn  up  toward  the  leg,  the  articular  sur- 
face of  the  astragalus  moving  slightly  backward  in  the  receiv- 
ing cavity.  Extension  is  the  reverse  of  flexion.  In  forced 
extension  the  narrow  part  of  the  astragalus  is  brought  forward 
into  the  broadest  part  of  the  receiving  cavity,  and  in  this  posi- 
tion a  slight  degree  of  lateral  movement  is  permitted. 

The  Articulations  of  the  Tarsus. 

The  articulations  of  the  tarsus  consist  of  the  articulation 
between  the  bones  of  each  row  and  the  union  of  the  two  rows. 


148  DESCRIPTIVE  ANATOMY. 

Calcaneo-Astragaloid  Articulation. 

The  two  bones  of  the  first  row  of  the  tarsus  are  held  together 
by  three  ligaments,  external,  posterior  and  interosseous. 

The  exierfial  calcaneo-astrag-aloid  ligament  extends  from 
the  outer  side  of  the  astragalus,  just  behind  and  internal  and 
as  far  as  the  anterior  fasciculus  of  the  external  lateral  of  the 
ankle,  to  the  outer  face  of  the  os  calcis.  It  lies  between  the 
anterior  and  middle  fasciculi  of  the  external  lateral. 

The  -posterior calcaneo-astragaloid  passes  from  the  posterior 
extremity  of  the  astragalus  to  the  contiguous  upper  aspect  of 
the  OS  calcis  and  is  but  a  continuation  of  the  protecting  fibres, 
called  the  posterior  ligament  of  the  ankle. 

The  interosseous  is  by  far  the  most  important  bond  of  union 
between  the  two  bones.  It  consists  of  a  large  number  of  fibres, 
filling  the  sinus  tarsi,  and  passing  directly  and  obliquely  be- 
tween the  surfaces  which  form  that  canal. 

The  Articulation  Between  the  Bones  of  the  Second  Row. 

The  bones  of  the  second  row  are  held  together  by  fibres 
passing  across  the  dorsal  and  plantar  faces  and  by  interosseous 
fibres  between  opposing  surfaces. 

The  Articulation  Between  the  two  Rows. 

The  two  rows  of  the  tarsus  are  held  together  by  three  sets 
of  ligaments,  two  sets  passing  from  the  os  calcis  to  the  cuboid 
and  scaphoid,  though  the  latter  does  not  articulate  with  it,  and 
one  set  passing  between  the  astragalus  and  scaphoid. 

Calcaneo-Cuboid  Articulation. 

The  ligaments  binding  the  os  calcis  to  the  cuboid  are  four, 
two  dorsal  and  two  plantar. 

The  superior  calcaneo-cuboid'v^  thin  and  narrow  and  passes 
between  the  contiguous  surfaces  of  the  bones  on  the  dorsum  of 
the  foot. 

The  internal  calcaneo-cuboid,  or  interosseous,  is  a  thick 
short  band  of  fibres  springing  from  the  depression  between 
the  OS  calcis  and  the  astragalus  and  inserted  into  the  inner 
side  of  the  cuboid.  At  its  origin  it  is  closely  blended  with  the 
superior  calcaneo-scaphoid. 


LIGAMENTS.  149 

The  lo72§'  inferior  calcaneo-ciiboid  ligament  is  attached  be- 
hind to  the  inferior  surface  of  the  os  calcis  from  its  posterior 
to  its  anterior  tubercle  ;  and  in  front  to  the  peroneal  ridge  on 
the  under  surface  of  the  cuboid  and  to  the  bases  of  the  meta- 
tarsal bones  of  the  second,  third  and  fourth  toes.  It  is  much 
thicker  and  stronger,  as  well  as  longer,  than  the  short  inferior 
calcaneo-cuboid,  which  lies  immediately  above  it. 

The  short  inferior  calcaneo-ciiboid  ligament  is  about  one 
inch  in  length.  It  is  attached  to  the  anterior  tubercle  of  the 
OS  calcis  and  to  the  bone  in  front  of  it  as  far  as  the  margin  of 
the  articular  surface  ;  and,  b}"  its  anterior  extremity,  to  the 
under  surface  of  the  cuboid  behind  the  peroneal  ridge. 

Calcaneo-Scaphoid  Ligaments. 

Connecting  the  os  calcis  and  scaphoid  are  two  ligaments, 
superior  and  inferior  calcaneo-scaphoid. 

The  superior,  one  arm  of  the  Y  lig-ament,  the  other  arm 
being  furnished  by  the  internal  calcaneo-cuboid,  passes  for- 
ward and  inward  from  the  front  upper  part  of  the  os  calcis  to 
the  scaphoid. 

The  inferior  calcaneo  scaphoid  is  much  stronger  than  the 
superior  and  passes  from  the  inner  front  aspect  of  the  os  calcis, 
beneath  the  head  of  the  astragalus,  to  the  lower  surface 
of  the  scaphoid. 

The  Astragalo-Scaphoid  Articulation. 

The  only  ligament  connecting  the  astragalus  and  the  scap- 
hoid is  the  superior  astrag-alo-scuphoid  which  is  thin  and  weak 
and  passes  from  the  neck  of  the  astragalus  to  the  upper  sur- 
face of  the  scaphoid. 

The  Tarso-Metatarsal  Articulation. 

The  first  metatarsal  bone  articulates  with  the  internal  cunei- 
form ;  the  second,  with  the  middle  cuneiform,  by  its  base,  and 
laterally  wMth  the  internal  and  external  cuneiform  bones,  being 
jammed  between  these  and  extending  farther  back  than  the 
other  metatarsal  bones  ;  the  third  articulates  with  the  external 
cuneiform,  and  the  fourth  and  fifth  with  the  cuboid. 

The  tarsus  is  held  to  the  metatarsus  by  dorsal "AXiA  plantar 
lig-amentous  fibres  and  by  three  interosseous  lig-aments — one 


150  DESCRIPTIVE  ANATOMY. 

from  the  internal  cuneiform  to  the  second  metatarsal  and  one 
from  the  external  cuneiform  to  the  third  metatarsal. 

The  metatarso-phalangeal,  the  inter-phcdang-eal  and  the 
'' inter metatarsaV  are  exactly  similar  to  those  of  the  hand. 

Costo- Vertebral  Articula,tion. 

The  parts  of  the  skeleton  which  enter  into  a  costo-vertebral 
articulation  are  the  posterior  extremity  of  the  rib,  the  body, 
and  transverse  process  of  a  dorsal  vertebra  and  the  interverte- 
bral disk. 

This  articulation  is  of  the  diarthrodial  class  and  the  arth- 
rodial  variety.  The  ligfaments  which  connect  the  head  of  the 
rib  with  the  vertebral  column  are  the  anterior  costo-vertebral, 
capsular  and  interarticular. 

The  anterior  costo-vertebral  is  attached  to  the  anterior  aspect 
of  the  head  of  the  rib,  and  radiates  in  three  bundles,  the  upper 
of  which  is  attached  to  the  body  of  the  vertebra  above,  the 
lower  to  the  vertebra  below,  and  the  middle  to  the  interverte- 
bral disk.  Owing"  to  the  divergence  of  its  fibres,  this  ligament 
is  known  as  the  stellate.  The  arrangement  differs  from  the 
foregoing  description  in  the  first,  eleventh  and  twelfth  ribs, 
where  the  ligament  is  attached  to  only  one  vertebra,  as  the 
articular  facet  is  furnished  wholly  by  one  vertebra. 

The  capsular  lig-ament  consists  of  a  few  scattered  fibres 
around  the  articulation. 

The  interarticular  lig-ament  is  attached  to  the  ridge  on  the 
head  of  the  riband  to  the  intervertebral  disk,  thus  dividing  the 
joint  into  two  parts,  each  furnished  with  a  separate  synovial  sac. 
For  the  reason  above  given,  the  first  eleventh  and  twelfth 
have  no  interarticular  ligament  and  but  one  synovial  sac. 

The  articulation  between  the  ribs  and  the  transverse  pro- 
cesses,known  as  the  costo-trans verse  articulation,  presents  three 
ligaments — anterior,  middle  and  posterior  costo-transverse. 

The  anterior  costo-transverse  extends  from  the  neck  of  the 
rib  to  the  transverse  process  above;  the  jfiiddle,  or  interosseous, 
extends  from  the  posterior  surface  of  the  neck  of  the  rib  di- 
rectly backward  to  the  transverse  process;  t\iQ. posterior  extends 
from  the  tubercle  of  the  rib  to  the  apex  of  the  transverse 
process. 


THE  VISCERA.  151 

THE  VISCERA. 

The  Alimentary  Canal  and  Appendages. 

.  The  alimentary  canal  beg-ins  at  the  mouth  and  ends  at  the 
anus,  the  intermediate  portions  being-  found  in  the  neck,  thorax 
and  abdomen.  In  the  neck  are  \h.<$.  fauces ,  pharynx  and  part 
of  the  aesophag-ns;  in  the  thorax  is  the  remaining-  portion 
of  the  oesophagus,  while  the  rest  of  the  canal  is  found  in  the 
abdomen. 

The  Mouth. 

The  mouth  beg-ins  at  the  lips  and  terminates  behind  in  a 
short  constricted  portion  called  the  fauces.  It  is  bounded 
above  by  the  hard  palate,  below  by  the  tong-ue  and  on  each 
side  by  the  cheeks. 

The  lips  are  two,  upper  and  lower,  separated  by  the  trans- 
verse labial  fissure.  Each  is  formed  chiefly  by  itsseg-ment  of 
the  orbicularis  oris  muscle,  covered  externally  by  skin  and 
internally  by  mucous  membrane,  a  concentric  fold  of  which, 
called  frcjenum  labii,  extending-  in  the  middle  line  from  each  lip 
to  the  g-um  behind.  The  cheek  consists  chiefly  of  the  buccin- 
ator muscle,  covered  externally  by  skin  and  internally  by  mu- 
cous membrane,  which  is  reflected  from  it  to  the  g-um  and 
presents,  opposite  to  the  second  molar  tooth  of  the  upper  jaw, 
the  opening-,  on  a  papilla,  of  Stenson's  duct  from  the  parotid 
g-land.  The  hard  palate  is  formed  anteriorly  by  the  meeting- 
in  the  middle  line  of  the  palate  processes  of  the  superior 
maxillary,  and  posteriorly  by  the  horizontal  plate  from  each 
palate  bone.  It  is  boundfed'"in  front  and  at  either  side  by  the 
aveolar  processes  of  the  superior  maxillary  bones,  containing- 
the  teeth  of  the  upper  jaw.  It  is  covered  by  mucous  membrane 
both  above  and  below,  forming-  the  floor  of  the  nasal  fossa} 
above  and  the  roof  of  the  mouth,  below  ;  on  the  latter  aspect 
the  mucous  membrane  is  roug-hened  by  g-lands,  called  palatal, 
and  is  continued  on  to  the  g-ums. 


152  DESCRIPTIVE  ANATOMY. 

The  floor  of  the  mouth  is  formed  by  the  anterior  two-thirds 
of  the  tong-ue,  the  posterior  third  the  tong-ue  forming-  the 
floor  of  the  fauces,  and,  below  that,  entering"  into  the  forma- 
tion of  the  anterior  wall  of  the  pharynx. 

The  tongue  is  flattened  from  above  downward,  is  conical 
in  shape  and  curved  in  direction,  being-  convex  above  antero- 
posteriorly,  and  extends  from  the  hyoid  bone  behind  to  the 
incisor  teeth  in  front,  its  base  being-  adherent  to  the  hyoid 
bone  and  its  apex  free  and  anterior. 

The  mucous  membrane  covering-  the  dorsum  of  the  tong-ue 
passes  around  the  sides  and  tip,  thus  enveloping-  most  of  the 
org-an,  and  leaves  the  lower  surface  to  become  continous  with 
that  lining-  the  g-um  of  the  lower  jaw.  In  contact  with  the 
posterior  part  of  the  dorsum  is  the  front  of  the  epig-lottis, 
which  is  held  to  it  by  three  folds  of  mucous  membrane,  the 
g-losso-epig-lottic  lig-aments,  middle  and  two  lateral. 

The  mucous  membrane  covering-  the  tong-ue  and  mouth  is 
continued  back  throug-h  the  fauces  to  blend  with  that  which 
lines  the  g-uUet. 

The  Fauces. 

'\^\\Q.  fauces,  or  isthmus  of  the  fauces,  is  that  narrow  part 
of  the  alimentary  canal  which  connects  the  mouth  posteriorly 
with  the  front  of  the  pharynx.  It  is  about  one  and  one-half 
inches  long-,  about  the  same  in  width,  and  rather  less  in  depth; 
the  size,  however,  varying-  g-reatly,  for  its  walls  are  chiefly 
formed  of  muscular  tissue,  which  is  peculiarly  subject  to 
reflex  action. 

The  roof  of  the  fauces  is  the  soft  palate;  the  floor  is  a  part 
of  the  dorsum  of  the  tong-ue;  the  sides  are  formed  by  two 
arching-  muscles,  and,  between  them,  the  tonsil  g-lands.  The 
muscle  in  front  is  the  palato-g-lossus,  forming-  the  anterior 
pillar  of  the  fauces;  that  behind  is  the  palato-pharyng-eus, 
forming-  the  posterior  pillar  of  the  fauces.  The  wall,  in  every 
aspect,  is  covered  by  mucous  membrane. 

Soft  Palate. 

The  soft  palate,  or  velum  penduluni  palati,  is  thin  and 
flattened  from  above  downward  and  forward.     It  is  attached 


THE  VISCERA.  153 

above  to  the  posterior  border  of  the  hard  palate  aad  hangs 
downward  and  backward,  separating-  the  fauces  from  the 
upper  part  of  the  pharynx.  It  is  prolong-ed,  in  the  middle  line 
below,  by  a  nipple-like  projection,  some  half  an  inch  long, 
called  the  uvula. 

Pharynx. 

Food,  in  order  to  reach  the  stomach,  passes  through  four 
successive  portions  of  the  alimentary  canal.  The  first  two  of 
these  have  been  described,  vix  :  the  mouth  and  fauces.  Leav- 
ing the  latter,  food  enters  the  pharynx,  whence  it  passes  to 
the  (esophagus,  in  which  the  pharynx  terminates,  and  the 
oesophagus  conveys  it  to  the  stomach. 

The  Pharynx  is  an  oblong  tube  situated  behind  the  larynx 
and  extending  from  the  lower  face  of  the  basilar  process  of 
the  occipital  to  the  fifth  cervical  vertebra  where  it  terminates 
in  the  oesophagus.  By  the  lower  margin  of  the  soft  palate  it 
is  divided  into  an  upper  portion,  establishing  communication 
between  the  nasal  cavities  and  the  larynx  below,  and  the  same 
cavities  and  the  middle  ear  on  the  side,  through  the  Eusta- 
schian  tube  ;  and  a  lower  portion  receiving  the  opening  of  the 
fauces  above  and  opening  into  the  oesophagus  below.  By  its 
musculo-aponeurotic  fibres  is  attached  to  all  of  the  surround- 
ing firm  structures,  base  of  the  occipital  bone,  pterygoid  pro- 
cesses of  the  sphenoid,  base  of  the  tongue,  hyoid  bone,  infe- 
rior maxillary  and  the  larynx.  From  the  occipital  down  to 
the  attachment  to  the  cartilages  of  the  larynx  it  is  a  large 
cavity  always  held  open  by  its  attachment  to  the  firm  sur- 
rounding structures  ;  but  from  the  larynx  to  its  termination, 
the  anterior  and  posterior  walls  are  more  or  less  closely  in 
contact,  except  during  the  act  of  swallowing.  The  muscular 
wall  is  deficient  above  and  behind,  where  a  concave  space  is 
seen  on  either  side  above  the  superior  constrictor  where  the 
pharyngeal  aponeurosis  is  thicker  than  elsewhere.  In  the 
anterior  wall,  above  the  soft  palate,  the  openings  of  the  poste- 
rior nares  are  seen  on  either  side  ;  while  further  out  and  oppo- 
site the  posterior  extremity  of  the  inferior  turbinated  bones, 
may    be     seen     the     openings    of    the     Kutaschian     tubes. 


154  DESCRIPTIVE  ANATOMY. 

Below  the  soft  palate  the  opening-  for  the  fauces  ocupies  the 
whole  of  the  anterior  wall,  while  below  this  is  the  antero-pos- 
terior  opening-  of  the  larynx,  behind  which  is  the  transverse, 
slit  like  opening  into  the  oesophag-us.  The  pharynx  is  sepa- 
rated from  the  front  of  the  bodies  of  the  upper  five  cervical 
vertebrae  by  a  layer  of  the  deep  cervical  fascia  and  some  loose 
connective  tissue.  It  is  about  four  and  one  half  inches  in 
length  and  tapers  as  it  descends. 

Structure. 

The  Alimentary  Canal  is  throughout  made  up  of  an  inter- 
nal mucous  coat,  resting  upon  a  thin  fibrous  layer  which  is  in 
turn  supported  by  muscular  fibres.  In  the  tongue,  soft 
palate  and  pharynx  the  muscular  coat  makes  up  the  bulk  of 
the  organ,  but  the  arrangement  differs  in  each  and  will  now 
be  described. 

The  Tong-iie  consists  of  two  sets  of  fibres,  called  intrinsic 
and  extrinsic  muscles  of  the  tongue.  The  extrinsic  muscular 
fibres  seek  points  of  attachment  to  surrounding  hard  parts, 
their  lingual  extremities  then  passing  into  the  tongue  to  blend 
with  the  intrinsic  muscles  found  there.  These  muscles  are 
the  following : 

Extrinsic 
Stylo-Glossus  Hyo-Glossus 

Palato-Glossus  Genio-Hyo-Glossus 

Intrinsic 
Superior  Lingualis  Inferior  Lingualis 

Vertical  Lingualis  Transverse  Lingualis 

The  Stylo-Glossus  arises  from  the  anterior  and  outer  side 
of  the  styloid  process  of  the  temporal  bone  near  its  apex,  and 
from  the  stylo-maxillary  ligament,  and  passing  downward, 
forward  and  slightly  inward  is  inserted  into  the  side  of  the 
tongue,  its  fibres  running  as  far  as  the  tip  where  they  meet 
with  the  muscle  of  the  opposite  side.  The  fibres  of  this  mus- 
cle blend  with  those  of  the  superior  and  inferior  lingualis. 

The  Hyo-Glossiis  is  a  flat  quadrilateral  muscle  which  arises 
from  the  side  of  the   body  and  both   cornua  of  the  hyoid  boue. 


THE  VISCERA.  155 

passes  directly  upward  and  is  inserted  into  the  whole  length 
of  the  tong-ue,  to  the  inner  side  of  the  Stylo-Glossus,  its  fibres 
blending^  with  the  vertical  ling-ualis. 

The  Palato-Glossus  is  a  small  muscle  found  occupying  the 
anterior  fold  of  the  fauces.  Arising-  in  the  soft  palate  it  pas- 
ses downward  and  inward  and  is  inserted  into  the  side  of  the 
tongue,  its  fibres  blending  with  the  transverse  lingualis. 

The  Goiio-Hyo-Glossus  is  a  thin,  radiated,  fan  shaped  mus- 
cle found  lying  close  beside  its  fellow  near  the  mid  line  and 
extending  from  base  to  apex  of  the  tongue.  It  arises  by  its 
apex  from  the  superior  genial  tubercles  and  is  inserted  into 
the  whole  length  of  the  tongue,  some  of  its  posterior  fibres 
being  attached  to  the  body  of  the  hyoid  bone.  Its  fibres  blend 
with  the  vertical  lingualis,  running  between  the  fibres  of  the 
longitudinal  and  transverse  lingualis. 

These  muscles  are  all,  except  the  Palato-Glossus,  supplied 
by  the  hypoglossal  nerve.  The  Palato-Glossus  is  supplied  by 
branches  from  the  pharyngeal  plexus.  The  lingual  artery  is 
the  source  of  the  blood. 

The  Tongue  I?,  divided  by  a  vertical  fibrous  septum  which 
occupies  the  middle  line  and  receives  the  insertion  of  the 
transverse  lingualis  muscle.  The  intrinsic  fibres,  largely  de- 
rived from  the  extrinsic,  are  two  superficial  sets,  superior  and 
inferior,  which  extend  from  base  to  apex  of  the  organ,  and  a 
transverse  and  vertical  set,  the  one  running  from  the  upper  to 
the  lower  surface  and  the  other  from  the  septum  to  the  lateral 
edges.  These  latter  fibres  are  mingled  with  each  other  so  as 
to  form  a  muscular  net  work  extending  throughout  the  tong-ue. 

Aclion.  The  intrinsic  muscles  can  act  only  to  produce  changes 
in  the  shape  of  the  tongue,  while  the  extrinsic  not  only  change 
the  shape  but  the  position  as  well.  The  Stylo- Glossiis  can 
draw  the  tongue  upward  and  backward,  or,  if  one  muscle  alone 
acts,  upward,  backward  and  toward  the  side  of  the  muscle 
acting.  The  Ifyo-Glossiis  draws  the  tongue  downward  and 
backward,  increasing  the  si/.e  of  the  fauces  and  aiding  the 
intrinsic  fibres  in  shortening  the  organ.  The  Pa/a/o-Glossiis 
widens  the  tongue  and   elevates   its   base,   depresses  the  soft 


156  DESCRIPTIVE  ANATOMY. 

palate  and  constricts  the  fauces  while  the  Genio-Hyo- Gloss  us 
draws  the  tong-ue  forward  by  its  posterior  fibres,  shortens  it 
by  the  approximation  of  posterior  and  anterior,  while  the  central 
fibres  depress  the  org-an  and  make  the  dorsal  face  concave. 
The  lower  fibres  can  draw  upward  and  forward  the  hyoid  bone. 

Muscles  of  the  Soft  Palate. 

L/evator  Palati  Tensor  Palati 

Azyg-os  Uvulse  Palato  Glossus 

Palato-Pharyng-eus 

The  Palato-Glossus  was  described  with  the  muscles  of  the 
tongue. 

Levator  Palati, 

The  levator  palati  arises  from  the  roug-h  surface  on  the 
basilar  face  of  the  petrous  bone,  near  its  apex,  and  from  the 
cartilag-inous  portion  of  the  E^ustachian  tube,  and  descends  to 
be  lost  in  the  soft  palate.     Its  name  indicates  its  action. 

Tensor  Palati. 

The  tensor  palati  is  a  small  muscle  which  forms  a  rig-ht 
ang-le  on  itself,  hence  its  synonym  of  circumflexus.  It  arises 
from  the  scaphoid  fossa  of  the  pteryg"oid  process,  from  the 
spinous  process  of  the  sphenoid  bone  and  from  the  cartilag-i- 
nous  portion  of  the  E)ustachian  tube,  and,  first  descending- 
vertically,  then  turning"  transversely  inward  around  the 
hamular  process,  it  spreads  out  into  a  broad  aponeurosis  in 
the  soft  palate.     Its  action  is  indicated  by  its  name. 

Azygos  Uvulse. 

From  the  posterior  termination  of  the  soft  palate  there  hang's 
pendulous,  in  the  centre,  a  short,  conical  mass  called  the 
uvula,  which,  when  dissected,  is  found  to  consist,  exteriorly, 
of  mucous  membrane  and,  interiorly,  of  a.  pair  of  minute 
muscles,  each  of  which,  arising  from  the  palate  spine,  descends 
beside  its  fellow  and  is  lost  in  the  mucous  membrane  of  the 
uvula.  These  two  muscles  were  formerly  considered  as  one, 
hence  their  name.  It  is  their  presence  in  the  uvula  which 
accounts  for  its  constant  and  varied  movement. 


THE  VISCERA.  157 

Palato-Pharyngeus. 

The  Palato-Pharyug-eiis  arises  in  the  soft  palate  and  passes 
downward  and  backward  to  enter  the  wall  of  the  pharynx, 
where  some  of  its  fibres  are  lost,  the  rest  being  inserted  into 
the  posterior  border  of  thethj^roid  cartilag-e.  Its  action  is  the 
same  as  the  preceding-  muscle  and  its  synonym  is  constrictor 
isthmii  faucium  posterior. 

The  Muscles  of  the  Pharynx. 

The  Pharynx  is  lined  by  raucous  membrane,  resting  on  a 
thin  fibrous  coat.  External  to  the  mucous  coat  is  a  muscular 
coat  consisting,  like  that  of  the  intestines,  of  circular  and  lon- 
gitudinal fibres,  but  differing  in  that  the  muscular  fibres  are 
here  red  and  not  pale,  and  are  gathered  into  bundles  which 
are  described  as  separate  muscles.  The  circular  fibres  are 
arranged  in  flattened  bundles  on  each  side,  each  bundle  inter- 
secting its  fellow  of  the  opposite  side  on  the  middle  of  the 
back  of  the  pharynx  where  they  form  a  raphe.  Each  pair  of 
bundles  overlaps  the  lower  edge  of  the  pair  above.  When 
traced  from  the  raphe  forward  it  is  seen  that  these  fibres  do 
not  encircle  the  entire  pharynx  but  pass  from  its  sides  to  seek 
firm  neighboring  points  of  attachment,  from  which  to  exert 
traction,  thus  leaving  the  front  of  the  pharynx  devoid  of  mus- 
cular fibres,  this  part  of  its  wall  being  formed  by  mucous 
membrane  alone.  The  larynx  resting  on  the  front  of  the 
pharynx,  is  in  contact  with  the  mucous  membrane  and  is  em- 
braced by  these  circular  fibres.  These  muscles,  from  their 
action,  are  known  as  the  constrictors  of  the  pharynx;  and  as 
there  are  three  separate  bundles,  they  are  described  as  supe- 
rior, middle  and  inferior  constrictors.  The  direction  of  their 
fibres  is  not  horizontally  backward  but  backward  and  upward. 

Inferior  Constrictor. 

The  inferior  constrictor  arises  from  the  oblique  line  on  the 
ala  of  the  thyroid  cartilage  and  surface  behind  it,  from  the 
side  of  the  cricoid  cartilage  and  from  the  two  upper  rings  of 
the  trachea.     It  runs  backward   and  upward,  its  upper  fibres 


158  DESCRIPTIVE  ANATOMY. 

passing*  obliquely  upward,  overlapping-  the  middle  constrictor 
and  is  inserted  into  the  raphe  of  the  pharynx. 

Middle  Constrictor. 

The  middle  constrictor  2lx\'s>q.^  from  bothcornua  of  the  hyoid 
bone,  and  from  the  stylo-hyoid  lig"ament,  a  fibrous  cord  extend- 
ing- from  the  hyoid  bone  to  the  styloid  process.  The  fibres 
radiate  somewhat,  spreading-  out  on  the  side  of  the  pharynx, 
and  are  inserted  into  the  raphe.  The  inferior  fibres  are  over- 
lapped by  the  inferior  constrictor,  and  the  superior  fibres 
overlap  the  superior  constrictor.  So  g-reat  is  this  overlapping- 
that  when  viewed  from  behind  but  little  of  the  superior  con- 
strictor can  be  seen,  the  raphe  of  the  middle  constrictor  ex- 
tending- to  the  basilar  process. 

Superior  Constrictor. 

The  superior  constrictor  lies  just  beneath  the  skull  and  is 
overlapped  by  the  middle.  It  arises  from  the  lower  one-third 
of  the  internal  pteryg-oid  plate,  from  its  hamuiar  process,  from 
the  pteryg-o-maxillary  lig-ament,  from  the  extremity  of  the 
molar  ridg-e  of  the  lower  jaw,  and  by  a  few  fibres  from  the 
side  of  the  tong-ue.  It  passes  backward  and  is  inserted  into  the 
raphe,  which  is  attached  to  the  basilar  process.  The  upper 
edg-e  of  this  muscle  presents  a  concave  border,  thus  leaving-  an 
arched  interval  between  it  and  the  skull  above,  over  which 
the  fibrous  tissue  beneath  the  mucous  membrane  ^f  the  phar- 
ynx extends  and  is  here  so  much  thickened  as  to  form  a  strong- 
fibrous  membrane. 

The  long-itudinal  fibres  of  the  pharynx  are,  like  the  circu- 
lar, g-athered  into  bundles,  of  which  there  are  two  pairs. 
These  are  described  as  distinct  muscles  arising-  from  points 
above  the  pharynx  and  inserted  into  it.  One  of  them,  the 
palato-pharyng-eus,  has  been  described  as  a  part  of  the  soft- 
palate  ;  the  other  is  known  as  the  stylo-pharyng-eus. 

Stylo-Pharyngeus. 

The  stylo-pharyng'eus  arises  from  the  inner  side  of  the  base 
of  the  styloid  process  and  descends  to  the  side  of  the  pharynx, 


THE  VISCERA.  159 

enteriiig-  its  wall  between  the  superior  and  middle  constrictors. 
Some  of  the  fibres  are  lost  in  the  pharynx,  while  some  are 
continued  to  the  posterior  border  of  the  thyroid  cartilag-e. 
Action — it  elevates  and  widens  the  pharynx. 

(Esophagus. 

The  CEsophagus  continues  the  course  of  the  alimentary 
canal  from  the  termination  of  the  pharynx,  at  the  commence- 
ment of  the  trachea  on  the  front  of  the  body  of  the  fifth  cervi- 
cal vertebra,  down  the  front  of  the  vertebral  column,  throu^-h 
the  neck  and  thorax,  to  pierce  the  diaphrag-m  at  the  (esopha- 
geal opening-,  opposite  the  tenth  dorsal  vertebra,  and  terminate 
at  the  cardiac  orifice  of  the  stomach.  It  is  about  nine  inches 
long-. 

In  structure  the  oesophag-us  resembles  the  pharynx,  but  its 
muscular  coat  is  not  arrang-ed  in  distinct  bundles.  It  is  the 
narrowest  part  of  the  alimentary^  canal,  but  the  most  muscular. 

Relations  of  Pharynx  and  (Esophagus. 

In  addition  to  the  structures  mentioned  as  opening-  into  or 
being-  connected  with  the  Pharynx,  it  has  important  relations 
to  structures  on  the  side  of  the  neck.  Thus  on  either  side  are 
the  muscles  attached  to  the  styloid  process  of  the  temporal 
and  internal  to  these  the  internal  jug-ular  vein  and  internal 
carotid  artery;  and,  between  these  two,  the  ninth,  tenth  and 
twelfth  nerves,  with  the  sympathetic  behind.  Below  the 
parotid  gland  the  external  carotid  artery  becomes  an  external 
relation,  while  the  ling-ual  lies  on  the  middle  constrictor. 
Below  the  upper  border  of  the  thyroid  cartilag-e  the  common 
carotid  becomes  the  external  relation. 

Relations  of  the  (Esophagus. 

The  relations  of  VtiQ CEsophagus  must  be  studied  in  the  neck 
and  in  the  thorax.  The  g-uUet  is  about  nine  or  ten  inches  in 
leng-th,  extending-  from  the  disk  between  the  fifth  and  sixth 
cervical  vertebrae  to  the  front  of  the  body  of  the  tenth  dorsal. 
It  is  not  a  straig-ht  tube  but  presents  antero-posterior  curves, 
corresponding-  to  the  curvatures  of  the  spinal  column.     There 


160  DESCRIPTIVE  ANATOMY. 

are  also  three  lateral  curvatures — two  to  the  left  and  one  to  the 
risfht.  At  its  commencement  it  lies  on  the  middle  line  of  the 
body  but  curves  to  the  left  until  it  reaches  the  root  of  the  neck. 
From  this  point  it  curves  to  the  rig^ht  until  it  ag-ain  reaches 
the  middle  line,  opposite  the  fifth  dorsal  vertebra,  and  from 
there  passes  steadily  to  the  left  ag-ain  until  it  terminates  oppo- 
site the  body  of  the  tenth  dorsal  vertebra. 

In  the  cervical,  and  upper  part  of  the  thoracic  portions,  the 
oesophag-us  is  separated  from  the  front  of  the  vertebral  column 
by  a  layer  of  fascia  and  by  the  long-us  colli  muscles,  particu- 
larly the  muscle  of  the  left  side.  In  the  lower  part  of  the 
thoracic  portion  it  is  more  widely  separated  from  the  vertebrae. 
The  trachea  lies  in  front  of  the  oesophagus  which  is  thus  shut 
off  from  contact  with  the  thyroid  gfland,  except  that  the  left 
lobe  of  the  latter  touches  the  oesophag-us  on  the  left  side.  The 
left  and  right  common  carotid  arteries  are  lateral  relations,  the 
left  being-  nearer  than  the  right.  At  the  root  of  the  neck  the 
thoracic  duct  is  a  left  and  slightly  posterior  relation  while 
the  left  recurrent  laryngeal  nerve  lies  in  the  g-roove  between 
the  trachea  and  oesophag-us. 

In  the  thorax  the  oesophagus  first  lies  behind  the  lower  part 
of  the  trachea,  which  separates  it  from  the  transverse  aorta, 
and  then  behind  the  bifurcation  of  the  trachea  and  the  left 
bronchus.  Below  the  trachea  the  pericardium  lies  on  the  front 
of  the  oesophag-us  to  its  termination.  Laterally  the  g-ullet  is 
in  contact  with  the  two  pleurae,  although  the  left  is  a  relation 
for  a  g-reater  distance  than  the  right.  To  the  rig-ht  above, 
and  separated  from  it  by  the  trachea,  is  the  innominate  artery, 
and  below  this,  the  vena  azyg-os  major  is  for  a  moment  to  the 
right  side.  On  the  left  is  the  left  common  carotid  artery, 
while  the  left  subclavian  is  a  more  distant  relation.  The 
descending  aorta  becomes  a  left  relation  at  the  lower  border  of 
the  fourth  dorsal  vertebra  and  remains  a  left  relation  to  the 
upper  border  of  the  seventh  dorsal,  below  which  point  the 
aorta  is  behind  and  finally  behind  and  to  the  right.  Behind 
are  the  longus  colli  muscle  above,  and  the  recurrent  laryngeal 
nerve  of  the  left  side  from  the  transverse  aorta  upward.  The 
thoracic  duct  is  a  posterior  relation  throughout  the  thoracic 


THE  VISCERA.  161 

portion,  but,  below  the  transverse  aorta,  lies  in  the  interval 
between  the  aorta  and  the  oesophag-us.  The  vena  azygos  major 
is  a  posterior  relation,  while  the  azyg-os  minor  crosses  behind, 
opposite  the  sixth  dorsal  vertebra.  The  right  pneumog*astric 
nerve  lies  behind  while  the  left  lies  in  front.  The  relation  to 
the  aorta  is  a  fourfold  one  and  should  be  thus  stated,  viz  ; 
the  oesophao-us  first  has  the  transverse  aorta  in  front,  then 
the  descendinor  aorta  first  to  its  left  side,  then  behind  and,  at 
the  termination  of  the  oesophao-us,  the  aorta  is  to  the  right 
and  behind. 

The  Abdominal  Viscera. 

The  cavity  of  the  abdomen  is  bounded  above  by  the  diaphragm, 
which  is  a  thin  arched  muscle  with  its  cavity  downwards,  form- 
ing the  floor  of  the  chest  and  the  roof  of  the  abdomen.  The 
floor  of  the  abdomen  is  the  floor  of  the  pelvis,  i.  e.  the  structures 
which  close  the  outlet  of  the  pelvis.  Occasionally  the  floor 
is  given  as  the  brim  of  the  true  pelvis  and  the  iliac  fossas,  the 
true  pelvis  being  then  considered  a  separate  cavity  Laterally 
and  in  front,  from  the  lower  ribs  above  to  the  ilium  below, 
the  abdominal  wall  is  formed  of  soft  tissues,  muscles,  &c. , 
and  is  the  soft,  fleshy  front  wall  of  the  belly.  At  its  upper 
part  the  cavity  is  partly  circumscribed  by  the  lower  ribs — the 
last  six  or  seven  ;  below,  by  the  bony  w^all  of  the  pelvis  ; 
behind,  by  the  lumbar  portion  of  the  vertebral  column  ;  while 
on  each  side  are,  above,  the  floating  ribs,  below,  the  pelvic 
wall,  and  between  the  two,  the  soft  tissues.  For  convenience 
of  description  the  abdomen  is  arbitrarily  divided  into  three 
zones,  and  each  of  these  into  three  regions,  by  two  horizontal 
and  two  vertical  imaginary  lines.  The  upper  horizontal  line 
is  drawn  between  the  extremities  of  the  ninth  ribs  :  the  lower 
between  the  anterior  superior  spinous  processes  of  the  ilia. 
The  vertical  lines,  one  on  each  side,  are  projected  upward 
from  the  middle  of  the  fold  of  the  groin. 

The  names  of  the  nine  regions  are  as  follows  :  The  central 
region  in  the  upper  zone  is  the  Epigastric,  the  one  on  either 
side  IIypocho}idriuc,  right  and  left ;  the  central  region  in  the 
middle  zone  Is  the  Umbilical,  the  one  on  either  side  Lumbar y 

Des  Anat — 11 


162  DESCRIPTIVE  ANATOMY. 

rig-ht  and  left ;  the  central  region  in  the  lower  zone  is  the 
Hypogastric,  the  one  on  either  side,  iliac,  rig-ht  and  left. 

The  contents,  of  the  abdomen  are  the  greater  part  of  the 
alimentary  canal,  the  accessory  org-ans  of  dig^estion — liver, 
spleen  and  pancreas — and  the  g^enito-urinary  org-ans — kidneys 
and  supra-renal  capsules,  the  bladder  and  its  appendag-es, 
prostate  gland,  seminal  vesicles  and  vas  deferens.  The 
testicles  are  considered  vv^ith  the  abdominal  viscera,  althoug-h, 
in  the '^Udult,  lying  in  the  scrotum,  outside  the  abdominal 
cavity.  In  the  female  there  are  the  uterus  and  its  appendages 
and  the  vagina.  E^nveloping  most  of  these  organs,  and  lining 
the  walls  of  the  cavity,  is  a  serous  membrane,  called  the 
peritoneum.  The  following  are  portions  of  the  alimentary 
canal  contained  in  the  abdomen:  1st,  iho. ^stomach;  2d,  small 
intestine ;  3d,  large  intestine.  The  stomach  is  the  dilated  part 
which  succeeds  the  oesophagus  and  is  about  twelve  inches 
long.  It  terminates,  about  the  line  which  separates  the  epi- 
gastric from  the  right  liypochandriac  reg-ion  in  the  small 
intestine.  The  small  intestine  is  divided  into  three  parts, 
diiodemun,  jejiiniun  and  ileum.  The  diiodemim  is  about  nine 
inches  long  ;  the  jejunum  and  ileum,  together  about  twenty 
feet,  the  jejunum  comprising  the  upper  two-fifths  and  the 
ileum  the  lower  three-fifths.  The  duodenum  is  again  subdi- 
vided into  three  portions,  viz  :  first  portion,  ascending,  or 
oblique  duodenum,  is  about  two  inches  long  and  terminates  at 
the  neck  of  the  gall  bladder,  on  the  lower  surf  ace  of  the  liver, 
in  the  right  hypochondriac  region  in  the  second  portion,  called 
the  descending  or  perpendicular  duodenum,  which  passes 
vertically  downward  for  about  three  inches  into  the  right 
lumbar  region,  about  on  a  level  with  the  upper  border  of  the 
fourth  lumbar  vertebra,  where  it  terminates  in  the  third  por- 
tion called  the  transverse  duodenum,  which  is  rather  more 
than  three  inches  long  and  crosses  the  front  of  the  vertebral 
column  obliquely  upward  and  terminates  at  the  left  side  of  the 
body  of  the  second  lumbar  vertebra,  in  the  jejunum. 

The  large  intestine  is  subdivided  into  three  portions  called 
caecum,  colon  and  rectum.     The   caecum   is   the   commencing 


THE  VISCERA.  163 

two  and  one-half  inches,  lies  in  the  rig-ht  iliac  fossa  and  termi- 
nates in  the  colon  at  the  opening-  of  the  small  intestine.  The 
colon  is  divided  into  the  ascending',  transverse  and  descending" 
colon  and  the  sigmoid  flexure.  The  ascending  passes  upward 
throug-h  the  rig-ht  lumbar  reg-ion  into  the  rig-ht  hypochondriac. 
At  the  under  surface  of  the  liver  it  curves  sharply  to  the  left, 
forming-  the  hepatic  flexure  of  the  colon,  and  becomes  the 
transverse  colon.  The  transverse  Q,<d\ovi  passes  downward  and 
to  the  left,  crosses  the  abdomen  between  the  epig-astric  and 
umbilical  reg-ions  and  rising"  into  the  left  hypochondriac  reg"ion 
forms  another  abrupt  curve  at  the  lower  end  of  the  spleen, 
called  the  splenic  flexure  of  the  colon,  and  becomes  the  descend- 
ing colon.  The  descending  colon  passes  downward  througfh 
the  left  lumbar  reg^ion  into  the  left  iliac  where  it  becomes  the 
sig^moid  flexure. 

The  sigmoid  flexure  is  that  portion  of  the  g-ut  which  passes 
from  the  left  iliac  fossa  into  the  pelvic  cavity  to  the  middle  of 
the  sacrum  where  it  becomes  the  rectum. 

The  colon  is  about  four  feet  in  length.  The  rectum  is  the 
last  four  inches  of  the  larg-e  intestine  and  terminates  the  ali- 
mentary canal  at  the  anus,  about  the  middle  of  the  floor  of  the 
pelvis. 

The  liver  lies  in  the  upper  zone  of  the  abdomen, 
stretching-  nearly  across  the  cavity  just  beneath  the  roof. 
The  spleen  is  in  the  left  hypochondriac  region.  The  pancreas 
lies  transversely  behind  the  stomach,  between  the  spleen  and 
perpendicular  duodenum,  crossing-  the  front  of  the  body  of  the 
first  lumbar  vertebra.  Each  of  the  two  kidneys  is  beside  the 
lumbar  portion  of  the  spinal  column,  on  the  front  of  the  pos- 
terior aVjdominal  wall.  The  uriiiary  bladder  "A-w^  its  append- 
ag-es  are  found  in  the  pelvis  just  behind  the  os  pubis.  The 
iderus  and  vagina  in  the  female,  are  interposed  between  the 
rectum  and  bladder. 

Reflections  of  the  Peritoneum. 

The  periloneiun,  being-  a  serous  membrane,  is  a  closed  sac, 
one  layer  covering-  the  viscera,  and  called  the  visceral  layer, 
and  the  other  lining  the  walls  and  called  the  parietal  layer. 


164  DESCRIPTIVE  ANATOMY. 

The  existence  of  the  peritoneum  renders  the  motions  of  the 
viscera  upon  one  another,  and  upon  the  abdominal  walls,  easy 
and  harmless  and  furnishes  bonds  of  connection  between  them 
and  the  walls  of  the  containing-  cavity.  Being-  a  closed  sac  its 
continuity  can  be  demonstrated  by  the  fact  that  in  following" 
it,  transversely  or  vertically,  it  can  be  traced  back  to  the  point 
of  departure.  The  folds  it  makes  from  above  downward  are 
the  most  important  and  will  be  first  stated. 

It  leaves  the  lower  surface  of  the  diaphragm  in  two  la^-ers, 
which  pass  to  the  upper  and  lower  edg-e  of  the  posterior 
border  of  the  liver.  The  upper  layer  covers  the  upper 
surface  of  the  liver,  curves  around  the  anterior  border 
and  coats  the  lower  surface  as  far  back  as  the  transverse 
fissure,  where  it  meets  the  lower  layer,  which  has  cov- 
ered the  lower  surface  from  the  posterior  border  to  the 
transverse  fissure.  The  two  layers,  having-  thus  enveloped 
the  liver,  leave  it  at  the  transverse  fissure  and  pass  down- 
ward to  the  stomach,  forming-  between  these  two  organs  the 
gastro-hepatic  or  the  lesser  omentum.  They  reach  the 
stomach  at  its  upper  border  and  divide,  one  passing-  over 
the  front  and  one  over  the  back,  and  meet  ag-ain  at  the  lower 
border  after  furnishing  a  coat  to  the  stomach.  The  two  layers 
leave  the  stomach  at  its  lower  border  and  pass  downward  to 
to  the  transverse  colon,  pass  over  it  without  touching  and 
descend  almost  to  the  brim  of  the  pelvis,  just  behind  the  ante- 
rior abdominal  wall  ;  they  then  reverse  their  course,  run 
upward,  just  posterior  to  their  descending  course,  reach  the 
transverse  colon,  and,  separating,  enclose  it.  That  part  of 
the  peritoneum  extending  between  the  lower  border  of  the 
stomach  and  the  transverse  colon  is  called  the  greater  omentum. 
The  two  layers,  having  enveloped  the  transverse  colon,  meet  at 
its  posterior  border  and  pass  back  to  the  posterior  abdominal 
wall,  where  they  form  the  transverse  mesocolon,  which  loosely 
holds  the  transverse  colon  to  the  posterior  abdominal  wall. 
The  two  layers  now  finally  separate;  one  goes  up  the  posterior 
abdominal  wall  to  the  lower  surface  of  the  diaphragm,  ^vhere 
its  course  was  first  taken  up,  thus  partially  enclosing  a  space 
behind  the  stomach  called  the  lesser  cavity  of  the  peritoneum, 


THE  VISCERA.  165 

which  communicates  with  the  g^eneral  cavity  through  an  opening- 
behind  the  oblique  duodenum,  called  the  foramen  of  Winslow; 
the  other  layer  passes  forward  to  envelope  the  coils  of  the 
jejunum  and  ilium  and  returns  to  the  posterior  abdominal 
wall,  forming-  a  double  layered  fold,  holding-  the  intestine  to 
the  abdominal  wall,  called  the  mesentery.  The  attachment  of 
the  mesentery  is  thus  stated :  from  the  left  side  of  the  body  of  the 
second  lumbar  vertebra  downward  and  to  the  right  to  the  rig-ht 
sacro-iliac  synchondrosis.  After  forming"  the  mesentery  the 
peritoneum  descends  the  posterior  abdominal  wall  to  the  brim 
of  the  pelvis  passes  down  its  posterior  wall,  covering  the  upper 
half  of  the  rectum  completely,  leaves  the  front  of  the  rectum 
an  inch  below  its  middle,  strikes  the  back  part  of  the  base  of 
the  bladder,  in  the  male,  covers  the  back,  sides  and  posterior 
half  of  the  top  of  the  bladder,  and  leaves  the  bladder  to  mount 
on  the  posterior  face  of  the  anterior  abdominal  wall  and  pass 
up  it  and  reach  its  starting  point  on  the  lower  surface  of  the 
diaphragm. 

In  the  female,  when  the  peritoneum  leaves  the  front  of 
the  rectum,  it  passes  to  the  lower  wall  of  the  vagina,  cover- 
ing its  upper  inch,  then  strikes  the  uterus  passing  up  -its 
back  and  turning  down  its  front  whence  it  passes  to  the  blad- 
der. In  mounting  over  the  top  of  the  uterus  it  also  passes 
over  the  ovary  and  its  ligament,  on  each  side,  thus  forming  on 
each  side  a  double  layered  fold  stretching  between  the  sides  of 
the  uterus  and  the  lateral  w^alls  of  the  pelvis  called  the  broad 
ligament  of  the  uterus.  Between  these  two  layers  are  the 
ovary  and  its  ligament,  the  round  ligament  of  the  uterus  and 
the  fallopian  tubes. 

Followed  transversely  around  the  abdomen,  about  its 
middle,  the  peritoneum  presents  the  following  folds  :  com- 
mencing on  the  anterior  abdominal  wall  it  can  be  followed  to 
the  posterior  abdominal  wall,  where  it  reaches  the  descend- 
ing colon  and  passes  over  it,  covering  it  from  half  to  three- 
fourths  around;  and,  leaving  it  at  a  corresponding  line  on  the 
inner  side,  it  reaches  the  vertebral  column  where  it  turns 
forward  to  envelope  the  folds  of  the  jejunum  and  ilium  and  to 
pass  back  on  itself  to  the  vertebral  column,  forming  the   nies- 


166  DESCRIPTIVE  ANATOMY. 

entery;  it  then  runs  out  on  the  posterior  abdominal  wall  to 
reach  the  ascending"  colon,  passes  over  its  front,  covering*  it 
from  half  to  three-fourths  around,  and,  leaving-  it,  reaches 
the  abdominal  wall  ag-ain  along-  which  it  runs  to  the  place  of 
departure. 

Relations  of  the  Abdominal  Viscera — Stomach. 

The  sto7nach  lies  in  the  upper  zone,  in  the  left  hypochondriac 
and  epigastric  reg-ions,  g-enerally  terminating- in  the  duodenum 
on  the  line  which  separates  the  epigastric  from  the  right 
hypochondriac  reg-ion,  but  occasionally  passing-  more  or  less 
into  the  latter.  Its  long-  axis  is  directed  from  above  down- 
ward, from  left  to  rig-ht  and  from  behind  forward;  one  surface 
looks  forward,  the  other  backward;  one  border,  the  shorter, 
or  lesser  curvature,  upward,  the  other,  the  long-,  or  greater 
curvature,  downward;  the  larg-e  end  is  to  the  left,  the  small, 
to  the  rig-ht.  It  is  continuous  with  the  duodenum  at  the  rig-ht 
end.  Its  upper  border  is  held  to  the  lower  surface  of  the  liver 
by  the  lesser  omentum;  its  lower  border  is  indirectly  held  to 
the  transverse  colon  by  the  g-reater  omentum;  its  left  end  is 
connected  with  the  spleen  by  the  g-astro-splenic  omentum. 
Above  it  are  the  diaphrag-m  and  the  left  lobe  of  the  liver;  be- 
low is  the  transverse  colon,  indirectly  held  to  it  by  the  g-reat 
omentum;  to  the  rig-ht  is  the  duodenum;  to  the  left  is  the 
spleen,  whose  concave  inner  surface  is  in  contact  with  the  con- 
vex left  extremity  of  the  stomach;  behind  is  the  pancreas, 
immediately  above  which  is  the  coeliac  axis  with  its  branches 
and  the  semi-lunar  g-ang-lia,  and  behind  these  is  the  abdominal 
aorta;  in  front  is  the  anterior  abdominal  wall,  partly  separated 
from  the  stomach  by  the  left  lobe  of  the  liver.  It  has  a  com- 
plete peritoneal  coat  which  forms  for  it  three  lig-aments,  the 
lesser  omentum  holding-  it  to  the  liver,  the  great  omentum  sus- 
pending the  transverse  colon  and  the  gastro-splenic  omentum 
binding  together  the  spleen  and  the  stomach. 

The  Oblique  Duodenum. 

The  oblique,  or  ascending-  duodenum,  commences  at  the 
right  extremity  of  the  stomach,  usually  on  the  line  which  sepa- 


THE  VISCERA.  167 

rates  the  epio-astrlc  from  the  rig-ht  hypochondriac  region,  and 
passes  upward  and  to  the  right,  in  the  latter  region,  to  termin- 
ate in  the  descending  duodenum  at  the  neck  of  the  gall  bladder 
on  the  lower  surface  of  the  liver.  It  lies  in  the  right  border 
of  the  lesser  omentum  and  has  behind  it  the  hepatic  artery, 
the  common  bile  duct  and  the  portal  vein.  The  duct  is 
furthest  to  the  right,  the  artery  to  the  left  while  the  vein  lies 
between  and  behind  the  two.  In  front  and  above  is  the  liver. 
It  is  completely  invested  by  peritoneum. 

The  Perpendicular  Duodenum. 

The  -pej-pendicular,  or  descejiding  duodenum,  commences  at 
the  termination  of  the  oblique  duodenum,  at  the  lower  surface 
of  the  liver,  at  the  end  of  the  gall  bladder  in  the  right  hypo- 
chondriac region,  and  descends  vertically  into  the  lumbar  re- 
gion to  terminate  in  the  transverse  duodenum,  about  on  a  level 
with  the  upper  border  of  the  fourth  lumbar  vertebra.  It  lies 
behind  the  peritoneum,  being  covered  by  it  only  in  front. 
Behind  it  has  the  right  kidney  and  in  front  the  ascending  colon; 
to  the  left  it  is  adherent  to  the  head  of  the  pancreas. 

The  Transverse  Duodenum. 

The  transverse  diiodouun  commences  where  the  oblique 
terminates,  in  the  right  lumbar  region,  on  a  level  with  the 
upper  border  of  the  body  of  the  fourth  lumbar  vertebra, 
and  passing  upward  and  to  the  left,  across  the  body  or 
the  third  lumbar  vertebra,  terminates  in  the  jejunum  at 
the  left  side  of  the  body  of  the  second  lumbar  vertebra. 
It  lies  behind  the  peritoneum,  between  the  diverging  layers 
of  the  transverse  meso-colon,  so  that  it  is  covered  by  perito- 
neum only  in  front.  Above  it  is  the  lower  border  of  the 
pancreas,  from  which  it  is  separated  by  the  superior  mesen- 
teric artery  and  vein;  in  front  is  the  transverse  colon. 

The  Jejunum  and  Ileum. 

The  remaining  twenty  feet  of  the  small  intestine,  follow- 
ing' the  duodenum ,  are  thrown  into  coils  called  the  convolu- 
tirms  of  the  small  intestine,  and  are  found  chiefly  in  the 
umbilical  and   hypog-astric  regions,  falling  off,   however,  into 


168  DESCRIPTIVE  ANATOMY. 

surroundiug-  regions,  some  being  always  found  in  the  pelvis 
between  the  rectum  and  bladder  in  the  male  and  the  rec- 
tnni  and  uterus  in  the  female.  The  jejunum  comprises  the 
upper  two-fifths  of  the  intestine  and  begins  where  the  duode- 
num terminates,  at  the  left  side  of  the  body  of  the  second 
lumbar  vertebra.  The  ileum  is  the  lower  three-fifths,  and 
terminates  in  the  right  iliac  region  by  opening  into  the  large 
intestine  two  and  one-half  inches  above  its  commencement. 

The  convolutions  are  completely  enveloped  by  the  perito- 
neum, which  holds  them  by  a  double-layered  fold  to  the  pos- 
terior abdominal  wall.  In  front  they  are  separated  from  the 
anterior  abdominal  wall  by  the  great  omentum  ;  above  is  the 
transverse  colon  ;  to  the  right  the  ascending,  to  the  left,  the 
descending  colon. 

The  Ccecum. 

The  caecum  is  the  commencement  of  the  large  intestine. 
It  is  two  and  one-half  inches  long  and  terminates  in  the  colon 
at  the  opening  of  the  small  intestine.  It  lies  in  the  right  iliac 
fossa  or  region,  and  is  generally  completely  invested  by  peri- 
toneum. Attached  to  it  is  the  vermiform  appendix,  a  blind 
tube  about  the  size  of  a  goose  quill  and  from  four  to  six  inches 
long.  It  opens  into  the  inner  back  wall  of  the  coecum,  just 
below  the  opening  of  the  ileum,  and  not  into  the  bottom. 
The  appendix  has  a  complete  peritoneal  coat  and  lies  slightly 
coiled  on  the  inner  side  of  the  coecum  and  just  below  the  ileum. 

In  front,  to  the  outer  side  and  behind  the  coecum  has  the 
abdominal  wall.  Internally  there  are  convolutions  of  the 
small  intestine  while  to  its  inner  and  posterior  aspect  are  the 
iliac  vessels,  separated  from  it,  however,  by  the  parietal  layer 
of  the  peritoneum.  , 

The  Ascending  Colon. 

The  ascending  colon  commences  where  the  coecum  termi- 
nates, in  the  right  iliac  region,  at  the  opening  for  the  ileum, 
and  passes  upward  through  the  right  lumbar  region  into  the 
right  hypochondriac  region  where  it  terminates  by  becoming- 
the  transverse  colon,  forming  the  hepatic  flexure  of  the  colon 
at  the  lower  surface  of  the   right  lobe  of  the  liver,  to  which 


THE  VISCERA.  169 

it  is  held  by  a  fold  of  the  peritoneum,  beings  covered  by  it  in 
front  from  half  to  three-fourths  around.  In  front  and  to  the 
outer  side  is  the  abdominal  wall  ;  to  the  inner  side,  the  convo- 
lutions of  the  small  intestine,  and  the  inferior  vena  cava ; 
behind,  the  perpendicular  duodenum  and  rig-ht  kidney,  the 
duodenum  being-  to  the  inner  and  posterior  aspect. 

The  Transverse  Colon. 

The  transverse  coloi  commences  at  the  termination  of  the 
ascending-  colon,  at  the  lower  surface  of  the  liver,  in  the  hepa- 
tic flexure  of  the  colon,  and  passes  obliquely  downward  and 
to  the  left,  crosses  the  abdomen  between  the  upper  and  middle 
zones,  and,  rising  into  the  left  hypochondriac  reg"ion,  termi- 
nates by  forming-  the  splenic-flexure  of  the  colon  at  the  lower 
end  of  the  spleen  and  becomes  the  descending-  colon.  Its 
course  is  curved  with  its  convexity  downward  and  forward. 
It  is  entirely  covered  by  peritoneum,  which  holds  it  by  a  long- 
double-layered  fold,  the  transverse  meso-colon,  to  the  poste- 
rior abdominal  wall  and  by  a  small  band  to  the  lower  end  of 
the  spleen.  It  is  indirectly  held  to  the  g-reater  curvature  of 
the  stomach  by  the  g-reat  omentum.  In  front  it  is  separated 
from  the  anterior  abdominal  wall  by  the  g-reat  omentum  ; 
behind  is  the  transverse  duodenum  ;  above  are  the  liver,  stom- 
ach and  spleen  ;  below,  the  convolutions  of  the  small  intestine. 

The  Descending  Colon. 

The  descendiiii*'  colon  begins  where  the  transverse  colon 
ceases,  in  the  left  hypochondriac  reg-ion  at  the  lower  end  of 
the  spleen,  and  passing-  downward  throug-h  the  left  lumbar 
reg-ion  terminates  in  the  left  iliac  region  by  becoming-  the  sig- 
moid flexure  of  the  colon.  It  lies  behind  the  peritoneum,  cov- 
ered bv  it  in  front  from  half  to  three-fourths  around.  To  its 
front  and  outer  side  is  the  abdominal  wall;  behind,  the  left 
kidney;  to  the  inner  side  are  the  convolutions  of  the  small 
intestine. 

The  Sigmoid  Flexure. 

The  sig-moid Jlcxurc  of  the  colon  begins  by  being  the  con- 
tinuation of  the  descending  colon  in  the  left  iliac  region  and. 


170  DBSCRIPTIVE  ANATOMY. 

passing-  down  into  the  pelvic  region  terminates  on  the  middle  of 
the  third  piece  of  the  sacrum  by  becoming-  the  rectum.  The  g"ut 
presents  many  differences  in  position,  but,  when  empty,  is 
usually  found  passing-  downward  and  to  the  rig-ht,  then  falling 
over  the  brim  of  the  pelvis  and  resting  against  its  own  lower 
portion  and  the  beg-inning  of  the  rectum.  It  is  completely  in- 
vested by  peritoneum,  which  holds  it  by  a  fold  of  variable 
length  to  the  abdominal  w^all.  It  crosses  the  pelvic  brim  in 
front  of  the  ureter,  from  which,  as  well  as  from  the  iliac  ves- 
sels, it  is  separated  by  peritoneum.  In  the  pelvis  it  lies  in 
front  of  the  internal  iliac  vessels  and  sacral  plexus  of  nerves 
and  comes  in  contact,  on  its  inner  side,  with  convolutions  of 
the  small  intestines,  the  side  of  its  own  terminal  portion  and 
the  side  of  the  rectum.  In  the  female  it  rests  against  the 
ovary,  uterus  and  vagina.  Between  it  and  the  vagina  and 
uterus,  in  the  female,  and  bladder  in  the  male,  are  interposed 
some  convolutions  of  the  small  intestines. 

The  Rectum. 

The  rectum  begins  by  being  the  continuation  of  the  sigmoid 
fixture  at  the  middle  of  the  third  piece  of  sacrum  and  termi- 
nates at  the  anus.  It  passes  straight  down  the  middle  line, 
conforming  to  the  curve  of  the  sacrum  and  coccyx,  until  it 
reaches  the  tip  of  the  latter  bone  when  it  turns  backward,  run- 
ning in  this  direction  downward  and  backward  for  about  an 
inch  and  a  quarter  when  it  terminates  at  the  anus.  At  its 
commencement  the  rectum  is  covered  by  peritoneum  about 
halfway  around,  but  the  peritoneum  gradually  leaves  the  sides 
of  the  gut  as  it  descends,  and,  after  a  course  of  about  an  inch, 
leaves  the  front  of  the  rectum  to  pass  to  the  bladder  in  the 
male,  or  the  back  of  the  vagina,  in  the  female.  That  portion 
of  the  rectum  which  is  covered  by  peritoneum  has  upon  its 
front  convolutions  of  the  small  intestines  which  separate  it 
from  the  bladder,  in  the  male,  or  the  uterus  and  vagina,  in  the 
female.  Behind,  the  rectum  rests  upon  the  front  of  the  sacrum 
from  which  it  is  separated  by  the  pyriformis  muscle,  and  the 
lower  sacrel  nerves,  In  front,  below  the  peritoneum,  it  has 
the  base  of  the  bladder,   prostate  gland,  seminal  vesicals  and 


THE  VISCERA.  171 

vas  deferens  and  is  crossed  on  its  side  by  the  ureters.  In  the 
female  the  vag-ina  rests  upon  the  front  of  the  g-ut,  at  first 
firmly  attached  to  it  but  separated  from  it  below  by  a  widen- 
ing-  interval  filled  in  by  the  perineal  body.  The  last  inch  and 
a  quarter  of  the  rectum  is  surrounded  by  fibres  of  the  levator 
ani  muscle  and  is  not  properlj^  an  abdominal  viscus,  lying"  in 
the  ischio-rectal  fossa. 

The  Liver. 

The  liver  is  found  in  the  upper  zone  of  the  abdomen,  the 
greater  part  being"  in  the  rigfht  hypochondriac  and  epigastric 
reg-ions,  but  projecting-,  to  a  g-reater  or  less  extent,  into  the 
left  hypochondriac.  Its  long-  axis  is  transverse  ;  its  sharp 
notched  border  is  in  front  and  below,  nearly  corresponding-  to 
the  lower  margin  of  the  ribs  on  the  right  ;  its  thick  border  is 
backwards,  resting  against  the  diaphragm  and  grooved  for 
the  inferior  vena  cava,  and  also,  near  the  left  end,  for  the 
oesophagus  ;  its  convex  surface  is  above  ;  its  large  end  is  to 
the  right. 

It  is  held  in  place  by  five  ligaments  and  is  connected  to  the 
stomach  by  the  lesser,  or  gastro-hepatic  omentum.  Four  of 
its  ligaments  are  formed  by  the  peritoneum  while  the  fifth, 
called  the  round  ligament,  is  the  remains  of  the  obliterated  um- 
bilical vein.  The  peritoneum  reaches  the  liver  by  two  very 
short  layers,  which  seize  the  one  the  upper  the  other  the 
lower  edge  of  its  posterior  border.  These  layers,  on  the  pos- 
terior border,  are  separated  by  a  considerable  triangular 
space  ;  but  at  each  end  they  come  together  and  form  the 
right  and  left  lateral  ligaments.  Between  these  lateral  liga- 
ments the  layers  surrounding  the  triangular  space  form  the 
coronary  ligament.  The  upper  layer  is  diverted  forward  from 
the  liver,  at  a  point  about  one-third  the  length  of  the  liver 
from  its  left  end,  across  the  upper  surface  of  the  liver  so  as  to 
surround  the  round  ligament  by  a  double-layered  fold  called 
the  suspensory  ligament,  or  the  longitudinal  ligament,  which 
holds  the  liver  to  the  diaphragm.  The  round  ligament  is  that 
part  of  the  obliterated  umbilical  vein  which  passes  backward 
from  the  anterior  abdominal  wall  to  the  notch  in  the  anterior 
border  of  the  liver,  lying  between  the  two  layers  of  the  longi- 


172  DESCRIPTIVE  ANATOMY. 

tudinal  lig-ament.  The  peritoneum  reaching-  the  liver  in  the 
manner  described,  passes  over  it,  one  layer  over  the  upper  sur- 
face, around  the  anterior  border  to  the  transverse  fissure  where 
it  meets  the  other  layer,  which  has  run  forward  on  the  lower 
surface  from  the  posterior  border,  thus  furnishing  an  almost 
complete  peritoneal  coat  for  the  organ. 

Above  the  liver  is  the  diaphrag-m,  which  separates  it  from 
the  thorax,  containing*  the  heart  and  lung's  ;  below  are,  from 
right  to  left,  the  right  kidney  and  supra-renal  capsule,  lying 
near  the  posterior  border  of  the  liver  ;  in  front  of  these,  and 
near  the  anterior  border,  the  hepatic  flexure  of  the  colon ; 
behind  and  to  the  left  of  this,  near  the  neck  of  the  gall  blad- 
der, the  oblique  duodenum  ;  to  the  left  of  this  the  upper  bor- 
der of  the  stomach,  held  to  the  liver  by  the  lesser  omentum, 
and,  to  the  left  of  this,  the  spleen,  suspended  from  the  under 
surface  of  the  diaphragm  by  the  suspensoTy  ligament.  The 
spleen  is  a  relation  only  when  the  liver  or  spleen,  is  much 
enlarged.  The  posterior  border  of  the  liver  has  upon  it  the 
inferior  vena  cava,  to  the  left  of  this  the  abdominal  aorta  and 
still  further  to  the  left  the  oesophagus.  On  its  under  surface 
should  be  mentioned  the  gall  bladder,  considered  with  the 
liver  itself. 

The  Spleen. 

T\iQsf)leen  is  confined  to  the  left  hypochondriac  region.  Its 
long  diameter  is  vertical;  its  thin  notched  border  is  anterior;  its 
smallest  end  is  below;  its  convex  surface,  external.  It  has  a 
complete  peritoneal  coat  and  is  held  in  position  by  folds  of  peri- 
toneum, onefold,  called  the  suspensor}^  ligament,  passing  from 
its  upper  end  to  the  diaphragm,  the  other,  called  the  gastro- 
splenic  omentum,  passing  from  its  inner  face  to  the  great  end 
of  the  stomach.  A  third  small  fold  extends  from  its  lower  end 
to  the  splenic  flexure  of  the  colon. 

Above  is  the  diaphragm  from  which  it  is  sometimes  separated 
by  the  liver;  below  is  the  splenic  flexure  of  the  colon;  behind 
the  lower  end  is  the  left  kidney  and  its  capsule;  in  front,  the 
anterior  abdominal  wall;  internal  to  it  are  the  great  end  of  the 
stomach  and  the  tail  of  the  pancreas;  externally  it  corresponds 


THE  VISCERA.  173 

to  the  ninth,  tenth  and  eleventh  ribs,  from  which  it  is  separated 
by  the  diaphragm,  the  left  pleura  and  the  lower  border  of  the 
left  lung. 

The  Pancreas. 

The  f)ancreas  extends  from  the  inner  face  of  the  spleen  on 
the  left  to  the  descending-  duodenum  on  the  right.  Its  long 
diameter  is  transverse;  its  large  end  to  the  right;  one  surface 
looks  forward,  the  other  backward;  one  border  is  above,  the 
other  below. 

It  rests  on  the  front  of  the  posterior  wall  of  the  abdomen, 
crossing  the  body  of  the  first  lumbar  vertebra.  It  is  behind 
the  peritoneum,  which  covers  it  only  in  front.  To  its  right  is 
the  perpendicular  duodenum,  to  which  it  is  closely  adherent;  to 
its  left  is  the  inner  face  of  the  spleen  to  which  its  tail  is  held 
by  the  peritoneum;  in  front  is  the  stomach;  behind  its  left  end 
is  the  left  kidney;  below  it  is  the  transverse  duodenum,  from 
w^hich  it  is  separated  by  the  superior  mesenteric  vessels.  Its 
relation  to  blood  vessels  are  very  complex,  and  may  be  given 
as  follows:  it  is  separated  from  the  vertebral  column  by  the 
abdominal  aorta,  w^hich  produces  thecoeliac  axis  on  a  level  with 
the  upper  border  of  the  head  of  the  pancreas  while  the  superior 
mesenteric  artery  is  emitted  just  behind  the  head;  the  latter 
descending  behind  the  pancreas,  to  pass  out  between  it  and 
the  transverse  duodenum. 

The  cfjeliac  axis,  resting  on  the  upper  border  of  the  head  of 
the  pancreas,  divides  into  three  branches,  one  of  which,  the 
splenic,  pursues  a  very  tortuous  course  along  its  upper  border 
to  the  inner  face  of  the  spleen.  This  artery  is  accompanied 
by  its  vein,  which  passes  to  the  right  from  the  spleen,  lying  in 
a  deep  groove  on  the  posterior  face  of  the  pancreas  just  below 
its  upper  border.  Behind  the  head  of  the  pancreas  the  splenic 
vein  unites  with  the  superior  mesenteric  vein,  which  ascends 
behind  the  pancreas  as  the  companion  of  its  artery,  the  two 
forming  the  portal  vein.  About  the  middle  of  its  course 
the  splenic  vein  receives  the  inferior  mesenteric  vein  which 
passes  behind  the  body  of  the  pancreas.  Surrounding  the 
coeliac  axis  are  the  two  semi-lunar  ganglia  of  the  sympathetic, 


174  DESCRIPTIVE  ANATOMY. 

giving-  off  the  numerous  branches  of  the  solar  plexus  of  nerves, 
which  are  in  close  relation  with  the  head  of  the  pancreas. 

The  Kidneys. 

The  kidneys  lie  on  the  front  of  the  posterior  abdominal  wall, 
extending-  from  about  the  eleventh  rib  downward  and  slig-htly 
outward  to  about  the  crest  of  the  ilium.  Therig-htis  perhaps 
a  little  lower  than  the  left,  reaching-  only  to  the  lower  border 
of  the  eleventh  rib  while  the  left  reaches  to  its  upper  border. 
The  kidneys  correspond  to  the  last  dorsal  and  the  upper  three 
lumbar  vertebrae.  They  lie  behind  the  peritoneum,  embedded 
in  a  considerable  mass  of  loose  connective  tissue,  which  usually 
contains  much  fat.  The  peritoneum  is  loosely  connected  to 
the  front  of  the  organ  by  this  tissue  and  can  easily  be  stripped 
off.  The  long-  diameter  of  the  kidney  is  from  above  downward 
and  slig-htly  outward;  one  face  looks  forward  and  slig-htly  out- 
ward, the  other  backward  and  slig-htly  inward  ;  the  upper  end 
is,  perhaps,  the  larg-er  ;  the  outer  border  is  convex,  the  inner 
concave.  Throug-h  most  of  its  extent  the  kidney  rests  on  the 
quadratus  lumborum  muscle,  separated  from  it  by  the  ante- 
rior lamella  of  the  posterior  aponeurosis,  of  the  transversalis 
muscle.  Along-  its  inner  edg-e  it  lies  on  the  psoas  mag-nus 
muscle,  and  behind  its  upper  part  is  the  diaphrag-m,  w^hich 
separates  it  from  the  pleura.  The  diaphrag-m  here  fre- 
quently presents  a  fissure  of  considerable  size,  where  the  mus- 
cular tissue  is  wanting-,  so  that,  in  this  event,  all  that  separates 
the  kidnev  from  the  pleura  is  a  little  loose  connective  tissue, 
li^ach  kidney  has  upon  its  upper,  inner,  front  part  the  supra- 
renal capsule.  The  outer  border  is  nearly  opposite  the  outer 
border  of  the  erect  or  spin«  muscle,  and  about  corresponds  to 
the  junction  of  the  posterior  third  with  the  anterior  two-thirds 
of  the  crest  of  the  ilium. 

The  rig-Jit  kidney  has  in  front  the  descending-  duodenum 
and  in  front  of  that  the  ascending-  colon  ;  along-  its  inner  bor- 
der is  the  ascending-  vena  cava  ;  its  upper  end  is  in  contact 
with  the  lower  surface  of  the  liver,  which  may  also  rest  on 
the  front  of  its  upper  part.  The  left  has  on  its  front  the 
descending-  colon  and,  at  its  upper  part,  the  lower  end  of  the 
spleen  the  tail  of  the  pancreas  and  the  g-reat  end  of  the  stomach. 


THE  VISCERA.  175 

The  Bladder,  in  the  Male. 

The  2(ri)iary  bladder  occupies  the  front  portion  of  the  pelvic 
cavity,  being-  confined  to  it  when  empty  or  nearly  so,  but  ris- 
ing out  of  it  according-  to  its  state  of  distension,  occasionally 
reaching-  the  level  of  the  umbilicus.  It  lies  just  behind  the 
S3'mph3^sis  pubis  with  its  long-  diameter  from  above  downward 
and  backward,  extending-  from  the  upper  border  of  the  sym- 
physis pubis,  or  a  point  in  the  linea  alba  between  it  and  the 
umbilicus,  varying  with  distension,  so  that,  if  prolonged,  it 
would  strike  the  lower  part  of  the  front  of  the  sacrum. 

The  large  end  of  the  bladder  is  below  and  looks  downward 
and  backward.  The  viscus  is  retained  in  position  by  its  liga- 
ments which  are  ten  in  number.  Five  of  these  are  called  false 
ligaments  and  are  furnished  by  peritoneum,  while  of  the  five 
true  ligaments  four  are  processes  of  fascia  and  one  is  the 
remains  of  a  foetal  structure,  called  the  urachus. 

The  peritoneum  leaves  the  front  of  the  rectum  about  three 
inches  above  the  anus,  and  sweeps  in  a  drooping  course  to  the 
back  part  of  the  base  of  the  bladder.  This  broad  fold,  ex- 
tending from  the  front  of  the  rectum  to  the  bladder,  is  spoken 
of  as  the  two  posterior  false  lig-aments.  The  division  between 
them  is  purely  arbitrary,  being  the  middle  line  of  the  body. 
On  each  side,  however,  the  fold  presents  an  antero-posterior 
ridge,  produced  by  the  passage  of  the  hypograstic  artery  from 
the  posterior  side  of  the  pelvic  wall  to  the  side  of  the  lower 
part  of  the  bladder,  the  artery  then  passing  up  the  side  of  the 
back  of  the  bladder  to  the  side  of  the  top,  whence  it  leaps  to 
the  anterior  abdominal  wall  and  approaching  its  fellow  of  the 
opposite  side,  makes  for  the  umbilicus. 

The  peritoneum,  reaching  the  bladder,  covers  the  back  part 
of  its  base,  the  back  of  the  bladder,  the  posterior  half  of  each 
side  and  the  posterior  half  of  the  top,  thence  passing  to  the 
anterior  abdominal  wall,  to  which  it  is  guided  by  the  urachus, 
and  the  obliterated  hypogastric  arteries.  That  part  of  the 
peritoneum  extending  from  the  middle  of  the  top  of  the  bladder 
to   the  anterior  abdominal   wall  is  called  the  superior  false 


176  DESCRIPTIVE  ANATONY. 

lig-ament;  and  that  part  on  each  side,  extending"  from  the  side 
of  the  bladder  to  the  lateral  wall  of  the  pelvis,  forms  the  lat- 
eral false  li^q-ament. 

The  four  remaining*  true  lig-aments  are  formed  by  the  pelvic 
fascia,  which  lines  the  pelvic  cavity  just  beneath  the  perito- 
neum. From  either  side  of  the  symphysis  pubis  a  process  of 
this  fascia  is  extended  to  the  lower  part  of  the  front  of  the 
bladder  and  prostate  gland,  these  two  being-  called  the  two 
anterior  true  ligaments  of  the  bladder.  From  the  lateral  wall 
of  the  pelvis,  on  each  side,  a  process  of  fascia  passes  to  the 
side  of  the  bladder,  the  two  being  known  as  the  two  lateral 
trite  lig'aments  of  the  bladder. 

The  front  of  the  bladder  is  separated  from  the  back  of  the 
symphysis  pubis  only  by  a  little  loose  connective  tissue.  The 
neck  of  the  bladder  is  received  into  the  back  part  of  the  pro- 
state g-land  and  is  continuous  with  the  urethra,  being*  about 
an  inch  behind  and  below  the  pubic  arch. 

The  posterior  face  of  the  bladder  is  separated  from  the  rec- 
tum usually  by  some  convolutions  of  the  small  intestine.  The 
base  of  the  bladder  rests  on  the  front  of  that  part  of  the  rec- 
tum which  is  found  descending-  the  front  of  the  sacrum,  and 
is  adherent  to  it.  Piercing-  the  posterior  part  of  the  base  of  the 
bladder  on  each  side  is  the  ureter,  the  two  being-  about  two 
inches  apart  each  having-  just  internal  to  it  the  vas  deferens, 
which,  entering-  the  abdomen  at  the  internal  abdominal  ring- 
passes  to  the  side  of  the  top  of  the  bladder,  descends  to  its 
posterior  face  runs  forward  and  inward  along-  its  base  to 
terminate  at  the  front  of  the  base  by  uniting-  with  the  duct, 
which  forms  the  seininal  vesicle  to  produce  the  ejaculatory 
duct.  The  seminal  vesicles  lie,  one  on  each  side,  on  the  side 
of  the  base  of  the  bladder.  They  are  pear-shaped,  the  base 
being-  behind  and  the  apex  forward  and  inward  at  the  back 
of  the  prostate  g-land. 

In  the  female  the  bladder,  in  general  terms,  occupies  the 
same  position  as  in  the  male.  There  are  no  prostate  glands, 
no  vas  deferens,  or  seminal  vesicles.  The  base  of  the  female 
bladder  rests  on  the  upper  wall  of  the  vagina  and  on  the  lower 


THE  VISCERA.  177 

part  of  the  front  of  the  uterus,  which  two  separate  it  from 
the  rectum.  Otherwise  the  relations  are  about  the  same  as 
in  the  male. 

Description  of  the  Separated  Viscera. 
The  Stomach. 

In  shape  the  stomach  is  a  curved  cone,  with  one  border 
shorter  than  the  other  and  its  two  sides,  called  anterior  and 
posterior  faces,  somewhat  flattened.  The  short  border  is 
known  as  the  lesser  curvature,  the  long-  as  the  g-reater  curva- 
ture. The  larg-e  end  of  the  cone  is  to  the  left  and  is  called 
the  splenic  end,  because  it  is  hugged  by  the  spleen.  At  the 
left  extremity  of  the  lesser  curvature,  two  or  three  inches  from 
the  left  end,  is  an  aperture  for  the  oesophagus,  called  the  car- 
diac orifice.  The  splenic  end  of  the  stomach  is  the  dilated  cul 
de  sac  bulging  beyond  this. 

The  rig-Jit  extremity  of  the  stomach  is  much  smaller  than  the 
splenic  end  and  is  called  the  pyloric  extremity,  because  the 
opening  of  this  end  of  the  stomach  in  the  duodenum  is  called 
the  pylorus.  It  is  the  smallest  part  of  the  alimentary  canal, 
being  only  an  inch  and  a  half  in  diameter.  The  position  of  the 
stomach  is  not  directly  transverse,  but  somewhat  oblique,  its 
long  diameter  being  from  above  dozunzuard,  forzuard,  and 
to  the  rig'ht  the  cardiac  orifice  being  on  a  higher  level  and  far- 
ther back  than  the  pyloric.  When  empty,  the  anterior  and 
posterior  faces  look  almost  directly  forward  and  backward  re- 
spectivel}'. 

The  longest  diameter  of  the  stomach  is  about  twelve  inches, 
and  it  can  receive  from  one  to  two  quarts  at  a  time. 

The  Duodenum. 

The  duodenum  succeeds  the  stomach.  It  is  about  nine  inches 
in  length  and  forms  a  horseshoe-shaped  curve  whose  convex- 
ity is  to  the  right.  It  is  divided  into  three  portions.  The 
first  portion,  beginning  at  the  stomach,  is  about  two  inches  in 
length  and  is  called  the  o/jlignc  portion.  It  passes  upward, 
backward  and  to  the  right.  The  second  portion,  called  the 
descending"  or  perpendicular  duodenum,  is  about  three  inches 
Des  Anat— 12 


178  DESCRIPTIVE  ANATOMY. 

long'  and  passes  downward.  The  third  portion,  called  the 
transverse  duodenum,  begins  where  the  descending-  terminates 
and  passing-  across  the  vertebral  column,  terminates  in  the  jeju- 
num,or  second  portion  of  the  small  intestine.  The  duodenum 
terminates  at  the  left  side  of  the  second  lumbar  vertebra  ;  but 
the  point  where  the  jejunum  becomes  the  ileum  is  arbitrary 
and  ill  defined.  The  jejunum  begins  where  the  duodenum 
terminates  and  comprises  the  upper  two-fifths  of  the  remain- 
der of  the  gut.  The  ileum  comprises  the  remaining  three- 
fifths  and  terminates  in  a  suddenly  dilated  portion  called  the 
large  intestine.  The  jejunum  and  ileum  together  are  about 
twenty  feet  long.  They  lie  coiled  up  chiefly  in  the  umbilical 
and  hypogastric  regions,  producing  an  appearance  somewhat 
similar  to  the  upper  surface  of  the  brain,  from  which  they  are 
called  the  convolutions  of  the  small  intestine. 

The  large  intestine  begins  by  a  sudden  dilation  just  below 
the  termination  of  the  small  intestine  in  the  right  iliac  region, 
and  extends  to  the  termination  of  the  alimentary  canal  at  the 
anal  orifice. 

The  large  intestine  is  about  five  feet  in  length.  It  is  sinu- 
ous in  its  course  and  is  divided  into  three  portions,  coecum, 
colon  and  rectum. 

The  entrance  of  the  ileum  is  not  into  the  extremity  of  the 
large  intestine  but  two  or  three  inches  above  its  commence- 
ment. The  blind  pouch  or  cul  de  sac,  which  extends  below 
this  orifice  is  called  the  coecum.  This  is  the  largest  portion 
of  the  large  intestine  ;  it  is  about  two  and  a  half  inches  in 
length,  lies  in  the  right  iliac  fossa,  is  continuous  wdth  the 
colon  above  and  has  projecting  from  its  lower,  inner  back 
part  a  tail-like  hollow  projection  called  the  vermiform  process, 
or  appendix,  which  is  from  four  to  six  inches  in  length  and 
lies  just  below  the  terminal  part  of  the  ileum,  its  cavity  being 
continuous  with  that  of  the  coecum. 

The  colon  is  the  second  portion  of  the  large  intestine.  It 
commences  at  the  entrance  of  the  ileum,  which  is  the  mark  of 
division  between  it  and  the  coecum,  in  the  right  iliac  region, 
and  passes  upward  through  the  right  lumbar  region  to  the 


THE  VISCERA.  •   179 

lower  surface  of  the  liver,  in  the  rig-ht  hypochondriac  region. 
This  portion  of  the  gut  is  called  the  asce)idi)i§  colon.  At  the 
lower  surface  of  the  liver  it  makes  a  bend  called  the  hepatic 
flexure  of  the  colon,  and  turns  to  the  left  across  the  abdominal 
cavit}^  This  portion  is  called  the  transverse  colon  and  its 
course  corresponds  to  the  superior  horizontal  line  of  the  abdo- 
men. At  the  lower  end  of  the  spleen,  in  the  left  hypochon- 
driac reg-ion,  the  colon  makes  another  bend,  called  the  splenic 
flexure,  and  turns  downward  to  pass  throug-h  the  left  lumbar 
region  to  the  left  iliac  fossa,  as  the  descending-  colon.  In  the 
left  iliac  fossa  it  makes  another  turn,  first  upward  and  to  the 
right  and  then  downward  and  to  the  left,  forming-  the  sig-moid 
dexiire,  which  terminates  at  the  brim  of  the  pelvis,  opposite 
to  the  left  sacro-iliac  s^^mphysis,  in  the  rectum.  The  rectum 
begins  where  the  sig-moid  flexure  terminates  and  passes  down- 
ward on  the  front  of  the  sacrum,  to  terminate  at  the  anus, 
being-  approximately   straig-ht  in  its   course — hence  its   name. 

Structure. 

The  following-  coats,  with  slight  exceptions,  are  common  to 
the  whole  of  the  alimentary  canal  found  in  the  abdomen: 

1st.  The  visceral  layer  of  the  peritoneum. 

2d.  The  interior  coat  is  mucous  membrane. 

3d.  Between  these  two  are  found  the  longitudinal  muscular 
fibres,  lying  next  to  the  serous  coat,  and 

4th.  The  circular,  next  to  the  mucous  coat. 

These  coats  are  held  to  one  another  by  interposed  connective 
tissue,  or  areolar  tissue.  Each  part,  also,  presents  some 
point,  peculiar  to  itself. 

The  stomach  has,  1st,  the  serous  coat  which,  besides  in- 
vesting- it,  passes  ofT  to  adjoining-  parts  forming- the  omenta  of 
the  stomach  which  seem  to  retain  it  in  its  position.  It  is  held 
to  the  liver  by  the  g-astro- hepatic,  or  lesser  omentum,  to  the 
spleen  by  the  gastro-splenic  omentum  and  to  the  transverse 
colon  by  the  g-astro-colic,  or  g-reater  omentum. 

2d  Just  beneath  the  serous  coat  is  the  long-itudinal  muscular 
coat. 


180  DESCRIPTIVE  ANATOMY. 

3d.  Just  beneath  this  is  the  circular  muscular  coat,  which  is 
thickest  toward  the  pyloric  extremity,  w^hile  the  longitudinal  is 
thickest  at  the  lesser  curvature.  The  fourth  coat  is  a  partial 
one,  of  oblique  muscular  fibres  which  diverg-e  from  the  cardiac 
end  of  the  stomach  beneath  the  circular  fibres  and  terminate 
before  reaching-  the  pyloric  orifice.  The  fifth  coat  is  the  inter- 
nal mucous  coat,  which,  when  the  stomach  is  empty,  is  thrown 
into  long-itudinal  ridg-es,  called  rug-ae,  which  disappear  when 
the  stomach  is  distended.  At  the  pylorus  the  mucous  coat  is 
thickened,  and  beneath  this  thickening-  is  an  ag-g-regation  of 
the  circular  fibres  so  as  to  produce  a  sudden  contraction  of  the 
tube.     This  appearance  is  known  as  the  pyloric  valve. 

The  duodemtm  has  four  coats:  1st,  serous;  2d,  long-itudinal 
muscular;  3d,  circular  muscular;  4th,  mucous  membrane.  In 
the  commencement  of  theg^ut  the  mucous  membrane  is  smooth, 
but  it  is  soon  thrown  into  folds,  which  pass  around  the  g^ut 
from  three-fourths  to  five-sixths  of  its  circumference;  called 
valvulas  conniventes.  These  valvulse  conniventes  are  continued 
down  into  the  jejunum  and  ileum,  but  g-radually  decrease  in 
size  and  in  the  ileum  are  inconspicuous.  They  are  permanent 
folds,  not  affected  by  distension. 

On  the  lower  inner  part  of  the  perpendicular  duodenum  is  a 
prominence  of  the  mucous  membrane,  called  a  papilla,  on 
which  is  seen  the  aperture  for  the  common  bile  duct  and  the 
pancreatic  duct. 

The  jejunum  and  the  ileum  have  the  same  coats,  in  the  same 
order,  as  the  duodenum.  Studding  the  inner  surface  of  the 
small  intestine  are  numberless  hair-like  microscopic  projections 
from  the  mucous  membrane  called  villi  ;  and  besides  these, 
and  numerous  mucous  follicles  which  have  their  seat  through- 
out the  small  intestine,  there  are  some  glandular  bodies  which 
have  special  seats. 

In  the  duodenum  there  are  numerous  small  glands,  about 
the  size  of  a  pin's  head,  lying  just  beneath  the  mucous  mem- 
brane and  opening  by  ducts  on  its  free  surface,  known  as  the 
glands  of  Brunner.  Scattered  throughout  the  small  intestine, 
but  much  more  numerous  in  the  lower  part  of  the  ileum,  are 


THE  VISCERA.  181 

small,  round,  grayish  bodies,  in  the  mucous  membrane,  which 
have  no  duct  and  are  called  solitary  g-lands.  In  the  lower  part 
of  the  ileum,  and  extending-  upward  ten  feet,  or  more — in  a 
few  instances  into  the  duodenum — are  found  a  number  of  dark, 
oblong",  g"ra3-ish  patches,  called  Peyerian  g-lands  or  Peyer's 
patches.  They  are  twenty  to  thirty  in  number.  Sometimes 
there  are  as  many  as  forty.  The  long*  diameter  of  these 
patches  is  in  the  direction  of  the  long-  diameter  of  the  g-ut. 
They  are  made  up  of  an  ag-g-reg-ation  of  the  solitary  glands 
and  become  diseased  in  typhoid  fever. 

The  opening-  of  the  small  intestine  into  the  larg-e  is  by 
means  of  a  horizontal  slit-like  opening-,  situated  on  the  inner 
side  of  the  larg-e  intestine  two  and  a  half  inches  above  its 
commencement,  and  g-uarded  by  a  valvular  arrang-ement  called 
the  ileo-coecal,  or  ileo-colic  valve.  This  valve  consists  of  two 
projections  into  the  cavity  of  the  large  intestine,  one  above 
and  the  other  below  the  button-hole-like  aperture,  each  seg-- 
ment  being-  a  fold  of  mucous  membrane  covering  circular  fibres 
of  muscular  tissue. 

The  larg-e  intestine,  like  the  small,  has  four  coats,  external 
serous,  internal  mucous  and,  between  these,  two  muscular, 
outer  long-itudinal,  inner,  circular.  From  the  commencement 
of  the  g-ut  to  the  rectum  the  longitudinal  coat  is  not  distributed 
uniformly  around  the  gut,  but  the  fibres  are  gathered  into 
three  narrow  flat  bands  placed  one  in  front,  one  on  the  back 
and  one  on  the  concave,  inner  side  of  the  gut.  These  bands 
are  shorter  than  the  other  coats  of  the  g-ut,  and  in  conse- 
quence the  other  tunics  are  thrown  into  folds  with  correspond- 
ing- depressions.  These  prominences  are  known  as  the  saculi 
of  the  larg-e  intestine.  Towards  the  termination  of  the  colon 
these  bands  begin  to  be  diffused,  and  in  the  rectum  the  long-itu- 
dinal fibres  are  ag-ain  distributed  and  of  equal  length  with  the 
other  coats.  The  mucous  membrane,  in  consequence  of  the 
shortness  of  the  long-itudinal  muscular  fibres,  is  also  thrown 
into  saculi.  Beneath  it,  especially  in  the  upper  part  of  the  gut, 
are  seen  a  number  of  solitary  glands  which  differ  from  those 
in  the  small  intestine  in  having-  a  duct. 


182  DESCRIPTIVE  ANATONY. 

The  rectum  presents  some  important  departures  from  the 
above  description.  It  is  divided  into  two  portions.  The  first 
portion  extends  from  the  commencement  of  the  gfut  until  it 
reaches  the  point  opposite  the  tip  of  the  coccyx  the  second  is 
the  last  inch  of  the  g^ut,  which  here  inclines  backward  to  term- 
inate at  the  anus.  The  rectum  presents  the  same  four  coats, 
in  the  same  order,  with  the  following-  exceptions:  The  serous 
coat  is  a  partial  one,  the  upper  half  of  the  g-ut  being-  entirely- 
surrounded  by  peritoneum  while  the  lower  half  is  covered  by 
it  for  only  an  inch  at  its  upper  front  part,  from  which  point  it 
mounts  to  the  bladder.  The  fibres  of  the  long-itudinal  muscular 
coat  becomes  much  more  distinct,  and  of  a  reddish  color,  in  the 
lower  part  of  the  g-ut;  and,  when  they  reach  its  extremity, 
they  do  not  stop  short,  but  turn  upward  to  run  along-  the  inner 
face  of  the  circular  fibres,  which  separate  them  from  the 
descending- long-itudinal  fibres  while  the  mucous  membrane  lies 
between  them  and  the  cavity  of  the  g-ut.  These  ascending- 
long-itudinal  fibres  are  g-athered  into  separate  bundles,  or 
columns,  which  pass  up  for  an  inch  or  two  before  ceasing- 
and  throw  the  mucous  membrane  into  ridg-es  with  intervening- 
depressions  called  rectal  pouches.  Towards  the  lower  extrem- 
ity of  the  rectum  the  fibres  of  the  circular  muscular  coat  are 
ag-g-regated  into  a  thickened  ring-,  internal  sphincter  ani,  and 
just  above  this  the  cavity  of  the  g-ut  is  considerably  dilated, 
forming-  a  capacious  reservior  in  cases  of  long-  continued 
constipation. 

The  Liver. 

The  liver  stretches  across  the  abdomen  just  beneath  its  roof, 
lying-  in  the  right  hypochondriac,  the  epig-astric  and  to  some 
extent,  the  -left  hypochondriac  region.  It  is  semi-ovoidal  in 
shape,  weig-hs  about  four  pounds,  is  about  twelve  inches  long-, 
six  broad  and  three  thick,  at  its  thickest  part  ;  in  color  it  is  a 
dull  red  with,  occasionally,  a  purplish,  or  yellowish  tingfe.  It 
is,  in  structure,  a  solid  glandular  organ.  For  study  it  is  divi- 
ded into  an  upper  and  a  lower  surface,  an  anterior  and  a  pos- 
terior border,  five  ligaments  and  an  excretory  apparatus. 

The  upper  surface  is  smooth  and  convex,  being-  moulded  on 
the  lower  surface  of  the  diaphrag-m.     It  presents  a  gflistening- 


THE  VISCERA.  183 

appearance  due  to  the  visceral  layer  of  peritoneum,  which  has 
been  traced.  The  peritoneum,  passing-  from  the  diaphragm  to 
the  liver  in  an  antero-posterior  fold,  strikes  the  liver  nearer 
the  left  than  the  rig-ht  extremity.  This  fold,  the  long-itudinal 
ligament,  is  a  mark  of  division  between  the  two  lobes,  all  that 
portion  lying-  to  the  right  being  known  as  the  right  lobe, 
while  the  much  smaller  portion,  lying  to  the  left  is  the 
left  lobe. 

The  anterior  border  is  thin  and  sharp  and  has  a  notch  at 
the  point  where  the  longitudinal  ligament  intersects  it,  which 
also  marks  the  division  between  the  lobes.  The  anterior 
border  is  just  above  the  lower  border  of  the  ribs,  though, 
when  the  liver  is  enlarged,  it  may  be  felt  through  the  abdomi- 
nal parietes. 

The  -posterior  border  is  thick  and  rounded  and  marked  b}"  a 
notch  where  it  is  intersected  by  the  longitudinal  ligament,  a 
third  mark  of  division  between  the  two  lobes.  The  openings 
for  the  hepatic  veins  are  found  on  this  border,  and  it  is 
grooved  for  the  inferior  vena  cava. 

The  lozver  surface  is  marked  from  before  backwards  by  a 
fissure  called  the  longitudinal,  which  is  just  opposite  the 
longitudinal  ligament  on  the  upper  surface,  and  extends 
from  the  notch  in  the  anterior  to  that  in  the  posterior 
border.  It  is  the  fourth  mark  of  division  between  the 
lobes.  The  lower  surface  of  the  right  lobe  presents  a  deep 
groove,  called  the  transverse  fissure,  which  runs  to  the  right 
from  the  longitudinal  fissure  which  it  strikes  about  at  its  pos- 
terior third.  In  this  fissure  are  found  the  hepatic  duct,  to 
the  right,  and  slighltly  in  front,  the  hepatic  artery  to  the 
left  and,  between  and  behind  the  two,  the  portal  vein.  That 
portion  of  the  longitudinal  fissure  which  is  behind  the  intersec- 
tion of  the  transverse  fissure,  is  called  the  venosus  fissure,  and 
the  portion  in  front  the  umbilical  fissure.  The  latter  is  fre- 
(juently  crossed  by  a  strip  of  liver  tissue,  called  the  pons 
hepatis.  Lying  in  front  of  the  transverse  fissure,  and  produc- 
ing an  impression  on  the  lower  surface  of  the  right  lobe,  is 
the  gall  bladder;  and  between  this  and  the  longitudinal  fissure 


184  DESCRIPTIVE  ANATOMY. 

is  a  square-shaped  portion  of  liver  tissue  called  the  lobus  qua- 
ratus,  whose  limits  are,  in  front,  the  anterior  border  of  the 
liver,  behind,  the  transverse  fissure,  to  the  rig-ht  the  g-all  blad- 
der to  the  left  the  long-itudinal  fissure.  Behind  the  transverse 
fissure  is  another  portion  of  liver  tissue,  which  has  received 
the  name  of  lobus  Spig-elii.  It  is  three  sided,  having-  in  front 
the  transverse  fissure,  to  the  left  the  venosus  portion  of  the 
long-itudinal  fissure  and  to  the  rig-ht  the  g-roove  made  by  the 
inferior  vena  cava. 

Running-  out  to  the  rig-ht  from  the  front  of  the  lobus  Spig-elii, 
just  behind  the  transverse  fissure,  is  a  ridg-e,  called  the  lobus 
caudatus.  Near  the  posterior  border  there  is  a  depression  on 
the  lov^er  surface  of  the  rig-ht  lobe  made  by  the  rig-ht  kidney 
and  its  suprarenal  capsule. 

The  liver  is  held  in  position  by  processes  of  peritoneum, 
called   ligaments,  which  are  five  in  number. 

The  longitudinal, ox  suspensory  I ig-am en t  consists  of  two  lay- 
ers of  peritoneum  which  pass  from  the  lower  surface  of  the 
diaphragm  to  the  upper  surface  of  the  liver.  These  two  layers 
separate  on  reaching  the  liver  and,  with  two  exceptions,  com- 
pletely invest  it.  One  exception  is  the  space  on  the  lower  sur- 
face, occupied  by  the  g-all  bladder,  for  the  peritoneum  leaps 
over  the  gall  bladder,  investing  it,  and  leaves  the  contiguous 
surfaces  of  g-all  bladder  uninvested.  The  other  exception  is 
found  at  the  posterior  border,  for  the  two  layers  here  diverg-e, 
to  form  the  rig-fit  and  left  lateral  lig-aments,  which  are  nothing- 
more  than  the  points  where  the  visceral  and  parietal  layers 
come  in  contact ;  and  between  the  two  diverg-ing-  layers,  on 
the  posterior  border,  there  is  a  triang'ular  space  which  has  no 
serous  coat.  The  two  layers,  as  they  skirt  this  space,  are 
known  as  the  coronary  ligament.  The  fifth  lig-ament  is  found 
as  a  rounded  cord  in  the  front  edg-e  of  the  longitudinal  liga- 
ment.    It  is  the  obliterated  umbilical  vein. 

The  excretory  apparatus  consists  of  a  series  of  ducts,  and  a 
reservoir,  called  the  gall  bladder. 

The  g-all  bladder  is  a  membranous  pyrif orm  sac,  lying  on  the 
lower  surface  of  the  right  lobe  of  the  liver,  its  large  end  lying 


THE  VISCERA.  185 

forward  and  usually  fallino-  short  of  the  anterior  border, 
thoug-h  occasionally  projecting-  beyond  it.  Its  small  end  lies 
backward  and  terminates  at  the  transverse  fissure  in  a  neck 
which  becomes  continuous  with  a  duct  called  the  cystic. 
This  duct  is  about  one-inch  long-  and  unites  with  the  duct  from 
the  liver  to  form  the  common  bile  duct.  The  g^all  bladder 
has  three  coats.  The  external  serous  coat  is  only  a  partial 
one,  since  it  passes  over  the  g"all  bladder  from  the  liver,  leav- 
ing- that  portion  next  the  liver  uninvested.  The  next  coat  is 
fibro-muscular. 

The  internal  coat  is  mucous,  and,  in  the  neck,  it  is  thrown 
into  spiral  folds,  so  that  liquid  in  following-  the  spiral  can 
flow  but  slowly. 

In  the  transverse  fissnre  two  ducts,  one  from  the  rig-ht  and 
one  from  the  left  lobe,  unite  to  form  the  hepatic  duct,  which 
is  about  two  inches  long-  and  descends  to  unite  with  the  cystic 
to  form  the  common  bile  duct — ductus  communis  choledochus 
— which  descends  for  about  three  inches  to  open  on  a  papilla 
on  the  lower  inner  part  of  the  perpendicular  duodenum. 

Structure. 

The  external  investment  of  the  liver  is  the  nearly  complete 
serous  coat.  Beneath  this  is  a  white  fibrous  coat  which  every- 
where covers  the  liver,  and  g-ives  off  numberless  processes 
which  pass  into  the  substance  of  the  liver  and  divide  it  into 
minute  subdivisions  called  lobules.  These  are  made  up  of 
the  proper  liver  substance. 

In  the  transverse  fissure  are  three  sets  of  vessels  which 
ramify  in  the  liver  to  fulfil  the  following-  offices  :  1st.  The 
hepatic  artery  carries  arterial  blood  to  the  liver.  2d.  The 
portal  vein  also  pours  a  stream  of  blood  into  the  org-an.  3d. 
The  hepatic  duct,  resulting-  from  the  coalescence  of  the 
smaller  ducts  from  the  lobules,  conveys  the  bile  away  from 
the  liver. 

When  traced  into  the  liver  these  vessels  are  found  associ- 
ated throug-hout  the  organ.  The  venous  blood  is  removed 
from  the  liver  by  means  of  a  fourth  set  of  vessels  called  the 
hepatic    veins,     which    result   from    ramifications   associated 


186  DESCRIPTIVE  ANATOMY. 

with  the  other  vessels  but  which  open,  by  three,  or  four  sep- 
arate apertures,  on  the  pDsterior  border  of  the  liver,  into  the 
inferior  vena  cava. 

The  Pancreas. 

The  pancreas  is  a  pale,  lobulated  g-land.  It  is  six  or  seven 
inches  long"  and  varies  in  thickness  from  an  inch  and  a  half  to 
less  than  half  an  inch.  It  weig-hs  about  three  ounces  and  lies 
horizontally  behind  the  stomach,  with  its  large  end  or  head 
embraced  by  the  concavity  of  the  descending-  duodendum,  and 
its  small  end  or  tail  in  contact  with  the  inner  aspect  of  the 
spleen.  It  crosses  the  body  of  the  first  lumbar  vertebra, 
which  renders  its  posterior  aspect  concave  whereas  its  ante- 
rior is  convex.  The  head  is  much  the  larg^er  portion  of  the 
org-an  and  sends  downward,  at  rig^ht  ang-les  to  the  rest  of  the 
organ,  a  considerable  projection  from  which  the  g-land  has 
been  likened  to  a  hammer.  The  head  also  furnishes  a  prom- 
inence backward  and  to  the  left  which  is  sometimes  called  the 
lesser  pancreas,  and  is  found  lying-  behind  the  superior  mes- 
enteric vessels. 

The  Pancreatic  Duct. 

The  pancreatic  juice  is  collected  and  conveyed  away  by  a 
duct  called  the  pancreatic,  or  canal  of  Wirsung;  which  com- 
mences in  the  tail  of  the  org-an  by  a  forked  orig-in.  The  two 
branches  soon  unite  and  the  resulting-  duct,  as  it  passes  to  the 
rig-ht  g-rows  by  momentary  accessions  until  it  reaches  the 
rig-ht  extremity  of  the  org-an,  where  it  pierces  the  coats  of  the 
perpendicular  duodendum  to  open  on  the  papilla  for  it  and 
the  common  bile  duct. 

Somewhere,  just  before  leaving-  the  pancreas,  it  receives 
the  duct  from  the  lesser  pancreas. 

In  structure  the  pancreas  is  a  lobulated  gland.  It  lies 
behind  the  peritoneum,  and,  consequently,  has  a  serous  coat 
only  in  front. 

The  Spleen. 

The  spleen  lies  vertically  in  the  left  hypochondriac  region. 
It  is  completely  invested  by  peritoneum,  which  forms  two 
folds  to  retain  it  in  position.     The  first  is  called  the  suspensory 


THE  VISCERA.  187 

ligament  and  suspends  the  spleen  by  its  upper  extremity  to 
the  lower  surface  of  the  diaphrag-m  ;  the  second,  the  gastro- 
splenic  omentum  passes  between  the  inner  surface  of  the  spleen, 
and  the  contiguous  large  end  of  the  stomach. 

In  color  the  spleen  is  a  dark  red,  in  shape,  semi-ovoidal,  in 
consistence,  extremely  fragile,  in  size,  about  six  inches  long, 
three  broad  and  one  and  a  half  thick,  in  weight,  about  seven 
ounces.  It  may  be  divided,  for  study,  into  two  surfaces,  two 
borders  and  two  extremities.  The  external  face  is  convex  to 
correspond  with  the  sweep  of  the  abdominal  wall  ;  the  inter- 
nal, flat,  or  perhaps,  concave,  to  hug  the  great  end  of  the 
stomach,  and  marked  about  its  centre  by  a  vertical  groove, 
called  the  hilum,  where  the  branches  of  the  splenic  artery  find 
ingress  and  the  vein  eg'ress,  and  where  the  gastro-splenic 
omentum  is  attached.  The  upper  extremity  is  much  larger 
than  the  lower,  which  is  thin  and  pointed.  The  posterior 
border  is  thick  and  rounded  ;  the  anterior,  thin,  sharp  and 
marked  by  one  or  more  notches. 

Structure. 

The  spleen  is  invested  by  two  coats,  an  external  serous  and, 
beneath  this,  a  fibro-elastic  coat,  from  the  inner  face  of  which 
are  sent  off  processes,  or  trabecular,  in  the  interspaces  of 
which  are  found  the  proper  splenic  fissure  or  parenchyma,  or 
splenic  pulp.  The  spleen  is  a  blood  vascular,  or  ductless 
gland,  and  whatever  it  elaborates  is  carried  off  without  the  aid 
of  a  special  apparatus. 

The  Kidneys. 

The  kidneys  are  a  pair  of  organs  found,  one  on  each  side  of 
the  vertebral  column  in  the  lumbar  region,  the  left  extending 
from  the  upper  border  of  the  eleventh  rib  to  the  crest  of  the 
ilium,  the  right  from  the  lower  border  of  the  same  rib,  being 
some  one-half  an  inch  lower  than  the  left.  They  about  corre- 
spond to  the  twelfth  dorsal  and  first  and  third  lumbar  vertebrae, 
and  diverge  somewhat  as  they  descend.  Each  is  embedded  in 
a  mass  of  fat  behind  the  peritoneum,  which  touches  them  only 
slightly  in  front.  Perched  on  the  upper,  inner  part  are  the 
two  supra-renal  capsules.     The    kidney  is  about  four  inches 


188  DESCRIPTIVE  ANATOMY. 

long",  two  broad  atid  one  thick.  It  is  peculiar  in  outline, 
hence  the  name  reniform.  The  anterior  surface  is  convex,  the 
posterior,  slightly  flattened  ;  the  upper  end  is  the  larger  ;  the 
outer  border  is  convex,  the  inner,  concave,  and  presents  a  deep 
depression,  called  the  liilum  of  the  kidney,  through  which  the 
duct  and  blood  vessels  pass,  in  the  following  order  :  the  renal 
vein  in  front,  the  duct,  or  ureter,  behind  and  the  renal  artery 
between  the  two.  The  hilum  leads  to  a  cavity  in  the  organ, 
called  the  sinus.     The  kidney  weighs  four  or  five  ounces. 

Structure. 

The  kidney  is  invested  by  a  fibrous  coat,  which  can  be 
easily  stripped  off,  thus  exposing  the  proper  tissue,  to  study 
which  the  kidney  should  be  split  longitudinally,  beginning  at 
its  external  border  and  passing  through  its  width.  It  is  then 
seen  to  consist  of  two  portions,  an  outer  layer,  red  in  color, 
which  forms  about  three  quarters  of  the  organ,  and  within 
this  is  a  portion  of  a  lighter  red  forming  the  remaining  fourth. 
The  outer  is  called  the  cortical,  the  inner  the  viedullary  ■por- 
tion. The  inner  portion  is  made  up  of  conical  masses  called 
pyramids  of  Malpig hi ;  they  are  arranged  with  their  bases 
toward  the  cortical  portion  and  their  apices  toward  the  hilum 
and  are  from  eight  to  eighteen  in  number.  ]j)ach  pyramid 
consists  of  hundreds  of  straight  tubules,  leading  from  the  cor- 
tical portion,  where  the  urine  is  secreted,  to  the  apex  or  papilla 
of  the  pyramid,  where  they  discharge  the  urine.  These  pyra- 
mids are  separated  by  prolongations  of  the  cortical  substance, 
which  projects  between  them. 

The  urine,  which  drops  from  the  papilla,  is  carried  off  by 
coalescing  ducts  having  different  names,  all  of  which  finally 
terminate  in  one  duct  called  the  ureter,  which  in  turn  opens 
into  the  urinary  bladder.  The  course  can  best  be  understood 
by  following  it  from  below  up.  Beginning  with  the  ureter 
we  find  that,  just  before  it  reaches  the  kidney,  it  begins  to 
enlarge  forming  what  is  called  the  pelvis  of  the  ureter,  which 
entering  at  the  hilum,  occupies  the  sinus  of  the  kidney.  The 
pelvis  of  the  ureter  soon  divides  into  three  tubes  called  infun- 
dihida,  one  infundibulum  collecting  the  urine  from  each  third 


THE  VISCERA.  189 

of  the  org-an.  Each  infuudibulum,  after  a  short  course, 
subdivides  into  a  number  of  short  tubes  called  calices,  each 
calyx  terminating-  by  surrounding-  the  apex  of  one  or  more 
pyramids.  The  course  of  the  urine,  then,  after  secretion  in 
the  cortical  portion  is  (1st.)  through  the  uriniferous  tubules, 
which  form  the  pyramids  of  Malpighi  (2d),  dropping-  from  the 
apex  or  papilla  it  falls  into  (3d)  the  calyx,  which  uniting-  with 
other  calices  from  its  third  of  the  organ,  forms  (4th)  an  infun- 
dibulum,  which  combines  with  the  other  two  infundibula  to 
form  (5th)  the  pelvis  of  the  ureter,  which  (6th)  contracts  to 
the  ureter  proper  which,  lastly,  opens  into  (7th)  the  bladder. 

The  Ureter. 

The  Ureter  commences  at  the  kidney  in  a  dilated  portion 
called  the  pelvis,  and,  contracting-  to  a  small  tube — about  the 
size  of  a  crow's  quill — passes  down  beside  the  vertebral  col- 
umn to  the  brim  of  the  pelvis,  descends  in  the  pelvis  behind 
the  bladder,  and  approaching-  its  fellow,  opens  into  the  back 
part  of  the  base  of  the  bladder.  The  apertures  for  the  two 
ureters  are  about  two  inches  apart,  and  the  tubes  pierce  the 
coats  of  the  bladder  in  an  oblique  direction.  The  leng-th  of 
the  ureter  is  from  sixteen  to  eighteen  inches. 

The  ureter — lying-  behind  the  peritoneum — consists  of  three 
coats,  an  external  fibrous  coat,  an  internal  mucous,  and, 
between  these,  an  external  long-itudinal  and  an  internal  circular 
muscular  coat.  This  description  applies  to  pelvis,  infuudibu- 
lum and  calyx.  Near  the  bladder  there  is  another  layer  of 
longitudinal  muscular  fibres  lying  between  the  circular  fibres 
and  the  mucous  membrane. 

The  Urinary  Bladder. 

The  bladder  is  the  reservoir  for  the  urine.  It  is  a  membra- 
nous sac  which  lies  in  the  pelvis,  just  in  front  of  the  rectum, 
in  the  male,  and  of  the  uterus  and  rag-ina  in  the  female.  Its 
shape,  when  distended,  is  ovoidal,  or  pyriform,  the  larg-e  end 
being-  below.  When  empty  it  is  flattened  against  the  pubes 
and  is  somewhat  triang-ular.  The  direction  of  its  long-  axis  is 
downward  and  backward.     The  capacity  of  the  bladder  is  very 


190  DESCRIPTIVE  ANATOMY. 

variable,  thoug-h,  in  health,  the  urine  is  voided  when  half  pint 
to  one  pint  has  been  secreted.  The  upper  third  of  the  organ, 
about,  is  called  the  superior  fiLudiis,  summit  or  apex  ;  its 
middle  third  the  body  ;  the  lower  third  the  base,  or  fundus. 
The  channel  throuo-h  which  the  urine  leaves  the  bladder  is 
called  the  urethra,  whose  aperture  is  seen  in  the  lower  front 
portion.  This  part  of  the  bladder  is  called  the  neck,  and  lies 
embedded  in  the  prostate  g-land.  In  structure  the  bladder 
consists  of  the  following-  coats :  1st.  The  internal  is  mucous 
membrane.  At  the  neck  of  the  bladder  there  is  a  slight 
prominence,  g-enerally  absent,  called  the  uvula  vesicce,  seen 
just  at  the  commencement  of  the  urethra.  Between  the  uvula 
vesicce  in  front,  as  its  apex,  and  the  opening's  for  the  ureters, 
as  its  posterior  ang-les,  there  is  a  triangular  space  called  the 
trigonum  vesica,  or  triang-le  of  the  bladder,  whose  base  is 
formed  by  a  line  drawm  between  the  opening's  for  the  ureters, 
and  whose  sides  are  formed  by  a  line  on  either  side  running- 
from  this  point  to  the  uvula  and  represented  by  a  ridg-e  in  the 
mucous  membrane  made  by  a  bundle  of  long-itudinal  fibres 
from  the  ureter.  This  space  is  by  far  the  most  sensitive  part 
of  the  bladder,  and  corresponds  to  a  similar  space  on  the  exte- 
rior of  the  base.  2d.  The  muscular  coat  is  held  to  the  mucous 
membrane  by  a  layer  of  areolar  tissue.  It  consists  of  long-itu- 
dinal and  circular  fibres,  the  long-itudinal  forming-  two  layers 
between  w^hich  are  found  the  circular.  The  circular  fibres, 
at  the  neck  of  the  bladder,  are  agg-reg-ated  into  a  considerable 
mass,  which  by  their  tonic  contraction,  keep  closed  the  opening- 
of  the  urethra.  3d.  The  external  coat  is  serous  and  incomplete. 
In  the  male  it  covers  the  summit,  sides,  posterior  aspect  and 
posterior  part  of  the  base  of  the  bladder,  leaving-  uncovered 
the  front  and  the  front  part  of  the  base. 

The  Urethra  in  the  Male. 

The  urethra  is  the  last  division  of  the  canal  which  the  urine 
traverses  in  seeking-  an  outlet  from  the  body.  It  commences 
at  the  neck  of  the  bladder  and  terminates  at  the  meatus  uri- 
narius,  its  opening-  on  the  free  extremity  of  the  penis.  Its 
leng-th  is  variously  estimated,  owing  to  the  varying  length  of 


THE  VISCERA.  191 

the  penis  which  it  tunnels.  It  is  divided  into  three  portions, 
the  prostatic,  which  begins  at  the  neck  of  the  bladder  and 
pierces  the  prostate  g-land  to  appear  at  its  apex  and  become 
the  second,  or  nicDibranoiis  portion,  which  passes  on  to  enter 
the  bulb  of  the  corpus  spongiosum  and  become  the  third,  or 
spongy  portion.  The  spong-y  portion  continues  through  the 
corpus  spongiosum  to  terminate  at  the  meatus  urinarius.  It 
is  the  longest  portion  and  the  most  variable  in  length.  The 
length  of  the  urethra  as  a  whole  is  usually  given  as  seven 
and  a  half  inches  of  which  the  prostatic  portion  occupies 
about  one  and  one-fourth  inches,  the  membranous  three- 
fourths  of  an  inch  and  the  spongy  portion  the  remainder. 
The  prostatic  portion  is  the  largest. 

The  Prostate  Gland. 

This  gland  is  a  small  horse  chesnut-shaped  body,  found  in 
the  male,  with  its  base  against  the  neck  of  the  bladder  and  its 
apex  projecting  forward.  Its  length  is  about  one  and  one- 
fourth  inches,  its  breadth  one  and  one-third,  and  its  depth 
about  one-half  inch.  It  is  invested  in  cellular  tissue  and  has 
a  proper  fibrous  capsule  ;  and  it  consists  of  interlacing  unstri- 
ated  muscular  fibres,  in  the  interstices  of  which  are  found 
the  follicles  of  the  gland,  which  secretes  a  milky  fluid.  It  is 
divided  into  three  lobes,  tvjo  latcraldLud.  an  inferior,  or  isthnins. 
Passing  through  it,  nearer  its  upper  than  its  lower  surface, 
is  the  prostatic  portion  of  the  urethra.  On  the  floor  of  this 
portion  of  the  urethra  is  seen  a  prominence  of  the  mucous 
membrane,  about  one-half  an  inch  long,  called  the  veru  mon- 
tanum.  On  either  side  of  this  prominence  is  a  depression  in 
the  floor  of  the  urethra,  called  the  sinus  prostaticus,  in  which 
are  found  some  ten  to  fifteen  minute  apertures — the  openings  of 
the  prostatic  follicles  ;  while  in  front  of  the  veru  montanum  is  a 
small  saccular  cavity,  projecting  backward,  called  the  sinus 
pocularis,  or  utriculus  prostaticus,  or  uterus  masculinus. 
Opening  on  either  side  of  the  orifice  of  this  sinus  is  seen  a 
small  aperture,  the  opening  of  the  ejaculatory  ducts,  which 
pass  back,  one  on  either  side,  to  two  lobulated  oblong  bodies, 
one  on  either  side,  just  behind  the  prostate  gland,  called 
seminal  vesicles. 


192  DESCRIPTIVE  ANATOMY. 


Seminal  Vesicles. 

E^acli  seininal  vesicle  is  a  reservoir  for  the  seminal  fluid,  and 
is  formed  of  a  tube,  about  the  size  of  a  g-oose  quill,  five  or  six 
inches  long-,  coiled  into  an  oblong-  mass,  which  lies  on  the 
lower  surface  of  the  base  of  the  bladder,  its  larg-e  end  project- 
ing backward  and  outward  from  its  fellow,  the  small  end 
being-  in  front  just  behind  the  prostate  gland  and  approaching- 
its  fellow.  The  posterior  extremities  are  about  two  inches 
apart,  and  a  line  drawn  from  one  to  the  other  is  the  base  of  a 
triangular  space,  w^hose  apex  is  at  the  prostate  gland,  which 
may  be  designated  the  intervesiciilar  triangle.  This  space 
is  devoid  of  peritoneum.  The  point  where  the  peritoneum 
strikes  the  base  of  the  bladder  corresponds  to  the  posterior 
boundary  of  this  triang-le,  whose  sides  are  formed  by  the  semi- 
nal vesicles  with  the  vas  deferens  of  either  side  lying-  internal 
to  them. 

Vas  Deferens. 

Commencing-  at  the  upper  extremity  of  the  testicle  the  vas 
deferens  forms  one  element  of  the  spermatic  cord,  the  others 
being-  blood  vessels,  nerves,  &c.,  which  ascends  to  the  upper 
border  of  the  pubes,  where  it  plung-es  into  the  anterior  abdom- 
inal wall,  through  the  external  abdominal  ring-,  then  outward, 
along-  the  ing-uinal  canal  to  the  internal  abdominal  ring-,  where 
it  turns  backward  throug-h  that  ring-  to  enter  the  abdominal 
cavity.  As  soon  as  the  cord  enters  the  abdomen  its  various 
constituents  disperse.  The  vas  deferens  passes  to  the  upper 
part  of  the  side  of  the  bladder,  thence  down  its  posterior  sur- 
face, along-  the  inner  edg-e  of  the  seminal  vesicles,  at  the  ante- 
rior extremity  of  which  it  is  joined  by  the  tube,  whose 
convolutions  form  the  seminal  vesicles,  and  the  two  form  the 
ejaculatory  duct. 

The  Ejaculatory  Duet. 

The  two  ejaculatory  ducts  lie  very  near  each  other  and  pass 
forward  and  upward,  throug-h  the  substance  of  the  prostate 
g-land,  for  about  three-quarters  of  an  inch,  to  open  on  the  sides 


THE  VISCERA.  193 

of  the  aperture  of  the  sinus  pocularis,  which  is  found  at  the 
base  of  the  veru  montanum,  in  the  floor  of  the  prostatic  portion 
of  the  urethra. 

The  Penis. 

The  penis  consists  of  three  cj^inders,  two,  lying-  side  by 
side  called  the  corpora  cavernosa^  and  one  in  a  g-roove  between 
these  known  as  the  corpus  spojigiosiim.  When  dissected  out 
the  corpora  cavernosa  are  seen  to  commence  by  attachment  to 
bone — the  ischio-pubic  rami — by  a  portion  called  the  crus 
which  terminates  posteriorly  in  a  pointed  extremity  ;  while 
anteriorl}^  it  increases  in  size  to  become  the  corpus  cavernosum. 
The  corpora  cavernosa  do  not  extend  to  the  extremity  of  the 
penis,  but  stop  a  little  behind  the  meatus  urinarius.  The 
corpus  spongiosum  beg^ins  by  a  dilated  portion  called  the  bulb, 
situated  between  the  crura,  into  which  the  membranous  portion 
of  the  urethra  passes  to  become  the  spong*y  portion.  It  then 
passes  forward,  tunnelled  by  the  urethra,  lying-  between  the 
corpora  cavernosa,  until  it  reaches  their  anterior  extremity, 
when  it  suddenly  dilates  into  a  considerable  mass,  which 
covers  the  extremity  of  the  corpora  cavernosa,  and  projects  in 
a  ridge  beyond  them.  This  dilated  extremity  is  called  the 
g-lans  penis  or  head.  The  g-lans  has  its  base  backward,  termi- 
nating- in  a  rounded  edg-e,  raised  above  the  surface  of  the 
corpora  cavernosa,  which  is  called  the  corona  glandis,  while 
the  constricted  portion  behind  it  is  called  the  neck.  From  the 
corona  the  glans  slopes  to  its  termination  around  the  meatus 
urinarius.  That  portion  of  the  penis  extending-  from  the 
crura,  or  rather  where  the  three  cylinders  come  in  close  rela- 
tion, forward  to  the  head,  is  called  the  body  of  the  org-an  ;  and 
the  two  crura  and  the  bulb  constitute  the  root  of  the  penis. 

Surrounding-,  and  loosely  adherent  to,  the  body  is  a  thin 
skin,  which  in  front  is  formed  into  a  fold,  movable  over  the 
glans  called  the  prepuce.  On  the  lower  aspect  of  the  g-lans 
the  prepuce  is  attached  by  a  process,  extending-  forward  to  the 
meatus  urinarius.     This  attached  portion  is  called  the  fra^num. 

Passing-  through  the  corpus  spongiosum  from  the  bulb 
behind  to  the  meatus  urinarius  in  front,  is  the  spongy  portion 

Des  Anat — 13 


194  DESCRIPTIVE  ANATOMY. 

of  the  urethra,  which,  just  before  its  termination  at  the  meatus, 
presents  a  considerable  dilation  called  the  fossa  naviciilaris . 
The  mucous  membrane  lining-  the  urethra  presents  many 
follicles,  called  lacunae,  opening  into  the  canal.  When  the 
mucous  membrane  reaches  the  meatus  it  is  continued  over  the 
g-lans  penis  and  the  deep  surface  of  the  prepuce. 

The  tissue  of  the  three  cylinders  is  that  known  as  erectile 
tissue.  E^ach  cylinder  is  enveloped  by  a  strong  fibrous  sheath, 
that  of  the  corpus  spongiosum  being  more  delicate  than  the 
others.  Within  this  sheath  the  structure  consists  of  inter- 
lacing bands  of  fibrous  tissue,  the  interspaces  between  which 
contain  dilated  blood  vessels,  which  when  turgid  with  blood, 
produce  erection.  The  two  corpora  cavernosa,  at  the  poste- 
rior part  of  the  body  of  the  organ,  are  separated  some  little 
distance  from  each  other,  but  as  they  pass  forward,  come 
much  closer  together,  for  the  fibrous  tissue  between  them  is 
thick  posteriorly,  whereas  in  front  it  is  thin  and  presents 
numerous  slit-like  interruptions  which  have  obtained  for  it 
the  name  of  septum  pecteneiform. 

The  Testicles— Testes. 

The  testicles  are  a  pair  of  small  org-ans  whose  function  it 
is  to  secrete  the  semen.  They  are  found  suspended  by  the 
spermatic  cord,  in  the  bag  called  the  scrotum,  separated  from 
each  other,  although  lying  side  by  side.  Each  testicle  weighs 
from  three-fourths  to  one  ounce  or  more  ;  it  is  an  inch  to  an 
inch  and  a  half  long,  about  an  inch  antero-posteriorly  and 
half  an  inch  transversely.  It  occupies  the  back  of  the  scrotum, 
its  position  being  from  above  downward  and  backward. 

The  scrotum  is  thus  constituted  :  1st,  an  external  covering 
of  skin  ;  2d,  beneath  this  a  musculo-fibrous  covering  called 
the  dartos ;  3d,  lining  the  interior  of  the  dartos,  and  also 
enveloping  the  testicle,  a  serous  membrane  called  the  tunica 
vaginalis.  That  portion  of  the  tunica  vaginalis  lining  the 
dartos  is  called  the  parietel,  and  that  lining  the  testicle  the 
/isceral  layer. 

There  are  two  cavities  in  the  scrotum  separated  by  a  sep- 
tum from  the  dartos  called  septum  scroti.  There  is  a  tunica 
vaginalis  for  each  testicle. 


THE  VISCERA.  195 

Structure  of  the  Testicle. 

When  the  visceral  layer  of  the  tunica  vag^inalis  is  removed 
we  find  beneath  a  bluish  white  fibrous  investment  of  the 
testicle  called  the  tunica  albug-inea.  This  is  much  thickened 
at  the  back  part,  where  it  is  called  the  mediastinum. 

Ivining-  the  inner  aspect  of  the  tunica  albuginea  is  a  reddish 
vascular  investment  called  the  tunica  vasculosa.  Lyinof  on 
the  posterior  aspect  of  the  testis  is  a  flattened  body  called  the 
epididymis,  w^hich  is  made  up  of  the  convolutions  of  the  tube 
conveying"  away  the  semen .  The  upper  portion  of  the  epididymis 
is  alone  permanently  connected  w'ith  the  testicle,  for  it  is  here 
that  the  ducts,  which  transmit  the  semen  from  the  testes, 
emero-e  and  unite  to  form  the  epididymis.  The  upper  portion 
of  the  epididymis  is  called  the  g-lobus  major,  the  lower  portion, 
which  terminates  in  the  vas  deferens,  the  g-lobus  minor.  The 
intermediate  portion  is  called  the  body.  The  semen  is  secreted 
in  w*hatare  called  the  lobules  of  the  testicles,  which  number 
from  250  to  400,  each  lobule  being-  separated  from  those  adja- 
cent by  septa  sent  in  from  the  tunica  albuginea,  which  septa, 
however,  are  covered  on  both  sides  by  a  layer  from  the  tunica 
vasculosa. 

Each  lobule  consists  of  the  convolutions  of  a  small  tube 
some  one-two  hundreth  of  an  inch  in  diameter,  arrang-ed  from 
before  backward  with  the  large  end  of  the  convoluted  mass  in 
front  and  the  small  end  behind  at  the  mediastinum,  where  many 
lobules  unite  toformasing-leduct,  which,  from  its  comparatively 
straig-ht  course,  is  called  the  rectum.  In  the  testis  there  are 
from  twenty  to  twenty-five  vasa  recta,  which  plunge  into  the 
mediastinum  and  there  unite  to  form  from  two  to  twelve  ducts, 
which  ascending-  throug-h  the  mediastinum  in  a  sinuous  course, 
are  called  collectively  the  rete  testis.  When  the  ducts  reach 
the  upper  extremity  of  the  mediastinum,  they  terminate  in 
from  nine  to  thirty  other  ducts,  called  vassa-efferentia,  each  of 
which  is  thrown  into  convolutions  assuming- a  conical  appear- 
ance which  are  known  as  coni  vasculosi  and  form  the  globus 
major.     The  bases  of  the  cones  terminate  in  large  ducts  which 


1%  DESCRIPTIVE  ANATONY. 

unite  in  the  body  of  the  epididymus  into  one  duct  whose  convo- 
lutions, some  twenty  feet  long,  form  the  body  and  g-lobus 
minor  of  the  epididymis  and  then  become  the  vas  deferens. 

The  continuous  course  of  the  semen  is  then,  lobule,  which 
may  be  composed  of  as  many  as  three  tubes,  vasa  recta,  rete 
testes,  vasa  efferentia,  coni  vasculosi,  epididymis,  body  and 
g-lobus  minor,  vas  deferens. 

The  JEiml  Apparatus. 

The  air  reaches  the  lung-s  from  the  throat  throug-h  a  tube 
which  has  received  different  names  in  its  various  parts.  It  is 
first  called  the  larynx,  then  the  trachea,  which,  opposite  the 
fifth  dorsal  vertebra,  divides  into  the  two  bronchi. 

The  Larynx. 

The  larynx  is  formed  upon  a  framework  of  separate  carti- 
lag"es  which  require  to  be  studied    under  individual  names. 
These  cartilag-es  are  as  follows  : 

Thyroid  Cricoid 

Two  Arytenoid  Two  Cornicula  Laryngis 

E^pig-lottis  Two  cuneiform 

Thyroid  Cartilage. 

The  thyroid  is  the  upper,  the  front  and  the  larg-est  cartilag^e 
of  the  larynx.  In  front  it  comes  to  an  acute  ang-le  and  produces 
the  prominence,  called  the  Adam's  apple,  pomum  Adami. 
Prom  this  acute,  or  receding-  angle,  it  passes  backward  and 
outward  on  either  side  in  a  quadrilateral  plate  called  the  ala 
of  the  thyroid  cartilag-e, 

E^ach  ala  presents  an  internal  and  external  surface,  superior 
inferior  and  posterior  border.  The  Outer  Surface  is  slig-htly 
concave  from  above  downward,  wider  above  than  below  and 
marked  by  an  oblique  ridg-e,  running  from  above  downward 
and  forward,  terminating-  at  each  end  in  a  prominence,  or 
tubercle. 

The  hiternal  Surface  is  nearly  flat,  slopes  outward  and 
backward  from  the  receding-  angle,  and  is  slig-htly  roug-hened 
for  muscular  attachment. 


THE  VISCERA.  197 

The  Superior  Border  is  sinuous  in  outline.  It  commences 
in  the  notch  found  marking-  the  upper  end  of  the  angle,  slopes 
first  upward  and  slightly  backward,  then  runs  nearly  back- 
ward to  terminate  in  a  prominent  projection  called  the  Supe- 
rior Cornu.  Just  before  reaching  the  superior  cornu  it  is 
marked  by  a  slight  depression.  This  border  is  rounded  and 
smooth. 

The  Inferior  Border  is  also  sinuous,  shorter  than  the  supe- 
rior, like  it  round  and  smooth  and  terminates  in  the  inferior 
cornu. 

The  Posterior  Border  is  rounded  and  free  and  prolonged 
both  above  and  below  into  processes  called  the  superior  and 
inferior  cornua,  each  terminated  by  a  tubercle.  The  superior 
cornu  is  the  longest. 

The  inferior  cor  mi  projects  downward  from  the  posterior 
border.  It  is  much  shorter  and  thicker  than  the  superior  and 
is  marked  on  its  inner  face  by  a  round,  flat  articular  facet  for 
a  similar  surface  on  the  cricoid  cartilage. 

Cricoid  Cartilage. 

The  cricoid  cartilage  is  a  ring  and  lies  supporting  the  thy- 
roid, between  whose  inferior  cornua  it  is  grasped.  It  is  nar- 
row in  front — not  more  than  one-fourth  of  an  inch  deep — but 
a  full  inch  in  depth  behind.  It  presents  an  upper  and  a  lower 
border,  but,  being  a  ring,  surfaces  are  not  ascribed  to  it.  The 
front  portion  of  its  exterior  is  marked  on  the  mid-line  by  a 
slight  ridge  on  each  side  of  which  is  a  small  impression  for  mus- 
cular attachment.  Behind  there  is  a  similar  ridge  in  the  mid- 
dle with  well  marked  muscular  impressions  on  either  side. 
In  front  of  these  impressions,  and  on  the  lateral  aspect,  a 
small,  round,  flat  articular  facet  is  seen  on  either  side  intended 
for  the  facets  on  the  inferior  cornua  of  the  thyroid. 

Its  Upper  Border  ^lo^e.'A  upward  and  backward,  presenting 
in  the  centre,  behind,  a  slight  notch,  and  on  either  side  of  this 
a  concavo-convex  articular  facet,  on  which  is  perched  another 
cartilage,  the  arytenoid.  The  anterior  portion  of  this  border 
is  smooth  and  rounded  for  liiramentous  attachment. 


198  DESCRIPTIVE  ANATOMY. 

The  Inferior  Border  is  nearly  straight,  thick  and  rounded 
and  sometimes  marked  by  a  deep  notch. 

It  is  held  by  lig-aments  to  the  first  ring-  of  the  Trachea. 
The  interior  of  the   ring  is  smooth  and  covered  by  mucous 

membrane. 

Arytenoid  Cartilages. 

The  arytenoid  cartilages  are  found  upon  the  cricoid,  between 
the  wings  of  the  thyroid  occupying  the  articular  facets  on  its 
upper  border.  It  is  triangular  in  shape  base  below  and  apex 
above,  and  is  divided  into  three  surfaces,  j)osterior,  anterior 
and  internal;  three  borders,  external  and  two  internal ;  and 
two  angles,  anterior  and  external. 

The  ^(9^/er2ory<:z<::e  is  concave  for  muscular  attachment;  the 
external  is  rough,  while  the  internal  is  smooth  and  flat  and 
faces  its  fellow  of  the  opposite  side. 

The  two  internal  borders  are  inconspicious,  forming  the 
anterior  and  posterior  boundaries  of  the  inner  face. 

The  external  border  is  rough  and  slopes  upward,  inward 
and  backward . 

The  external  ang-le,  points  outward  and  backward  and  is 
rough  and  thick.     It  is  called  the  muscular  process. 

The  anterior  angle,  thinner  and  longer,  is  know  as  the  vocal 
process. 

The  afex  points  upward  and  inward  and  is  surmounted  by 
a  small  cartilage,  the  cornicula  laryngis. 

The  base,  directed  downward,  is  concavo-convex  for  articu- 
lation with  the  similar  facet  on  the  upper  border  of  the 
cricoid. 

The  Cornicula  Laryng-is  are  two  small  cartilages  found 
perched  upon  the  apex  of  the  arytenoids.  The  cuneiform  are 
small  masses  found  in  the  aryteno-epiglottideau  fold. 

Epiglottis. 

The  epiglottis  lies  just  above  the  receding  angle  of  the  thy- 
roid cartilage.  It  is  leaf  shaped,  its  apex  downward  and  for- 
ward and  its  base,  which  presents  a  slight  notch,  upward  and 
backward  and  lying  at  the  base  of  the  tongue.  Its  upper  end 
may  be  sometimes  seen  by  looking  down  the  throat. 


THE  VISCERA.  199 

It  is  covered  by  mucous  membrane  which  holds  it  to  surround- 
ing- structures  and,  when  this  is  stripped  off,  is  seen  to  present 
a  convex  anterior  and  a  concave  posterior  surface,  the  latter 
marked  by  depressions  for  small  g-lands. 

Ligaments  of  the  Larynx. 

The  cartilag-es  of  the  Larynx  are  held  tog-ether  by  lig-aments 
some  of  which,  like  lig-aments  at  other  articulations,  serve 
only  the  purposes  of  such  fibres  ;  while  other  so-called  lig'a- 
ments  are  specialized  bands  employed  in  producing-  sound. 

The  hyoid  bone  lies  just  above  the  superior  border  of  the 
thyroid  cartilag-e  and  passing-  between  them  is  an  unbroken 
membrane  called  the  thyro-hyoidean,  and  in  each  of  the  poste- 
rior edg-es  of  this  membrane  a  rounded  cord,  which  passes 
from  the  superior  cornu  of  the  thyroid  cartilag-e  to  the  posterior 
extremity  of  the  hyoid  bone. 

The  thyro-hyoid  membrane  is  a  thin  sheet  of  fibrous  tissue 
which  is  attached  below  to  the  upper  border  of  the  th3"roid 
cartilag-e,  extending-  from  one  cornu  to  the  other  and  filling-  in 
the  notch  above  the  ang-le.  Above,  it  passes  beyond  the  lower 
border  of  the  hyoid  and  is  attached  to  the  upper  border  and 
posterior  surface  of  the  body  of  that  bone,  extending-  on  either 
side  to  the  cornua.  Between  the  membrane  and  the  posterior 
surface  of  the  body  of  the  Hyoid  there  is  a  pouch-like  space 
left. 

The  thyroid  and  cricoid  cartilag-es  are  held  tog-ether  by  the 
following-  lig-aments.  The  extremity  of  each  inferior  cornu  of 
the  thyroid  cartilag-e  is  held  to  the  facet  on  the  side  of  the  cri- 
coid by  a  capsular  lig-ament.  The  considerable  interval  which 
exists  in  front  between  the  lower  border  of  the  thyroid  and 
upper  border  of  the  cricoid  is  closed  in  by  a  fan-shaped  yellow 
elastic  membrane,  called  the  crico-thyroid  membrane,  which 
is  attached  below  to  the  upper  border  of  the  cricoid  and  above 
to  the  lower  border  of  the  thyroid  for  about  one-fourth  of  an 
inch  on  each  side  of  the  middle  line  and  then  presents  a  free 
edg-e,  covered  by  mucous  membrane,  which  posteriorly  is 
attached  to  the  anterior  ang-le  of  the  base  of  the  arytenoid 
cartilag-e,  forming-  the  lower,  or  true  vocal  chords. 


200  DESCRIPTIVE  ANATOMY. 

When  viewed'  from  above  the  vocal  chords  appear  to  be 
separate  bands  of  elastic  fibres,  each  arising-  from  the  receding 
angle  of  the  Thyroid  and  passing  backward,  diverging  from 
its  fellow,  to  be  attached  to  the  vocal  process  of  the  Arytenoid. 
They  are  called  inferior  thyro-arytenoid  ligaments,  or  true 
vocal  chords. 

Each  Arytenoid  is  bound  to  the  Cricoid  by  a  capsular  liga- 
ment which  holds  the  cartilages  together,  forming  a  concavo- 
convex  articulation  lined  by  a  synovial  sac.  In  addition  to  the 
inferior  thyro-arytenoid  ligaments,  mentioned  above,  another 
pair,  the  superior  thyro-arytenoid,  or  false  vocal  chords,  ex- 
tend from  just  above  the  base  of  the  Arytenoid  to  the  receding 
angle  of  the  Thyroid. 

Passing  now  to  the  epiglottis  we  find  its  apex  held  to  the 
receding  angle  of  the  thyroid  by  a  narrow  ligament  called 
thyro-epiglottic.  It  is  connected  to  the  hyoid  bone  by  a  liga- 
ment called  hyo-epiglottic,  which  is  attached  to  the  epiglottis  on 
its  front  edge  near  its  apex.  The  back  of  the  tongue  and  the 
epiglottis  are  connected  by  three  ligaments,  one  in  the  centre 
and  one  on  each  side,  called  glosso-epiglottic,  middle  and  lateral. 

Muscles  of  the  Larynx. 

The  movements  on  each  other  of  the  separate  cartilages 
which  constitute  the  larynx  are  mainly  effected  by  five  pairs 
of  small  muscles  C2,lled  the  instrinsic  muscles  of  the  larynx. 

Crico-Thyroid  Posterior  Crico-Arytenoid 

Arytenoid  Lateral  Crico-Arytenoid 

Thyro- Arytenoid 

Crico-Thyroid. 

The  crico-thyroid  is  a  small  triangular  muscle  lying  on  the 
side  of  the  cricoid  cartilag-e  and  partly  covering  the  crico- 
thyroid membrane,  which  appearS'On  the  mid-line  in  the  inter- 
val between  the  two  muscles. 

It  arises  from  the  front  and  side  of  the  cricoid  cartilage  and, 
passing  upward,  backward  and  outward,  is  inserted  into  the 
lower  border  of  the  thyroid  cartilage  from  the  median  line  in 
front  to  the  inferior  cornu. 


THE  VISCERA.  201 

Action — When  the  thyroid  cartilage  is  fixed  by  the  thj^ro- 
hyoid  muscle,  the  crico-thyroid  will  draw  up  the  front  of  the 
cricoid,  depressing-  the  back  which  carries  the  arytenoid  with 
it,  thus  elongating  and  rendering  tense  the  vocal  chords. 

Posterior  Crico- Arytenoid. 

The  Posterior  Crico-arytenoid  arises  from  the  depression 
on  the  posterior  aspect  of  the  cricoid  cartilage  and,  passing 
upward,  outward  and  forward,  is  inserted  into  the  outer  angle 
of  the  base  of  the  arytenoid. 

Action — B\^  drawing  on  the  muscular  process,  or  outer  angle 
of  the  arytenoid,  it  rotates  that  cartilage  around  a  vertical  axis, 
carr3'ing  the  vocal  processes  away  from  each  other,  widening 
the  glottis  and,  to  some  extent,  tightening  the  chords. 

Lateral  Crico-Arytenoid. 

The  Lateral  Crico-arytenoid  arises  from  the  side  of  the 
cricoid  cartilage,  and,  passing  upward,  outward  and  backward, 
is  inserted   into  the  outer  angle  of  the  base  of  the  arytenoid, 

Action — It  is  the  antagonist  of  the  posterior  crico-arytenoid. 
drawing  the  outer  angle  of  the  ar3^tenoid  forward,  approxi- 
mating the  vocal  processes  and  rendering  the  vocal  chords  loose. 

Arytenoid. 

The  Arytenoid  is  a  single  muscle  which  arises  from  the  con- 
cave posterior  face  of  one  arytenoid  cartilage  and  passes  trans- 
versely across  the  interval  between  the  two  to  be  inserted  into 
the  same  part  of  the  opposite  cartilage. 

Action — By  drawing  the  arytenoid  cartilages  towards  each 
other,  it  narrows  the  glottis. 

Thyro- Arytenoid. 

The  1  hyro-arytenoid  arises  from  the  receding  angle  of  the 
thyroid  cartilage  just  beside  and  external  to  the  attachment 
of  the  vocal  chorcls,  and,  passing  backward,  parallel  with  the 
vocal  cord  is  inserted  into  the  anterior  angle  of  the  base  of  the 
arytenoid  cartilage.  This  muscle  runs  parallel  wnth  the  true 
vocal  chord,  into  which  some  of  its  fibres  are  inserted. 

Action — By  drawing  the  muscular  process  forward,  turning 
the  vocal  process  inward  and  for  wad,   it   narrows  the  glottis 


202  DESCRIPTIVE  ANATOMY. 

and  relaxes  the  vocal   chord.     Those  fibres  inserted  into  the 
vocal  chord,  change  the  tension  of  the  chord  at  different  points. 

Vessels  and  Nerves.  The  superior  and  inferior  thyroid 
arteries  supply  these  muscles.  The  superior  laryng-eal  nerve 
supplies  the  crico-thyroid.  The  inferior,  or  recurrent  laryn- 
g^eal  supplies  the  other  muscles. 

The  larynx  is  lined  by  mucous  membrane  continuous  with 
that  of  the  mouth.  Looking-  into  the  cavity  of  the  larynx 
from  below,  at  a  certain  point,  the  cavity  is  suddenly  narrowed 
by  two  ridges,  one  on  either  side,  running-  from  before,  where 
they  are  close  together,  backward,  diverging  as  they  g"o  and 
leaving  a  triangular  interval  between  them  called  the  chink 
of  the  glottis,  or  rima  glottidis;  these  ridges  are  produced  by 
the  inferior-thyro  arytenoid  ligaments,  or  true  vocal  chords. 
Reversing  the  larynx  and  looking  into  its  cavit}"  from  above, 
the  opening  into  it  from  the  pharynx  is  seen  to  be  limited  by 
the  epiglottis  which  projects  upward  and  backward.  Over 
the  opening,  posteriorly,  are  seen  the  arytenoid  cartilages  ; 
laterally  are  folds  of  mucous  membrane,  the  ventricular  bands; 
the  opening  is  heart  shaped  with  its  broad  end  in  front. 
Down  in  the  cavity  are  seen  the  ridges  on  each  side,  one  above 
the  other.  The  lower  pair  are  those  seen  from  below,  the  up- 
per correspond  to  the  superior  thyro-arytenoid  ligaments  and 
are  the  false  vocal  chords.  As  they  are  much  less  prominent 
than  the  true  cords,  they  cannot  be  seen  when  the  cavity  is 
viewed  from  below.  The  space  between  the  false  vocal  chords 
bears  no  name,  but  the  similar  and  smaller  space  between  the 
true  chords  is  known  as  the  rima  glottidis.  On  each  side  of 
the  glottis  is  another  space  formed  by  a  recess  in  the  walls  of 
the  larynx,  between  the  true  and  the  false  vocal  chords,  which 
is  called  the  ventricle  of  the  lar^mx,  and  this  space  is  continued 
up  on  the  outside  of  the  false  vocal  chords,  between  it  and  the 
wall  of  the  larvnx  for  some  distance.  This  prolongation  of 
the  cavity  is  known  as  the  sacculus  laryngis. 

It  will  be  seen,  therefore,  that  the  larynx  is  divisible  into 
three  portions  by  the  position  of  the  vocal  chords,  the 
upper  portion  presenting  the  epiglottis,  the  folds  of  mucous 


THE  VISCERA.  203 

membrane  extending*  between  the  arytenoid  and  the  epiglottis 
and  containing-  the  pyriform  sacculus  laryng-is  which  runs  up 
just  internal  to  its  outer  wall.  This  space  extends  to  the  supe- 
rior thyro-arytenoid  membrane. 

The  second  subdivision. is  the  space  between  the  vocal  chords 
and  contains  four  opening-s,  viz:  one  above,  leading*  from  the 
upper  to  the  middle  compartment, — being-  the  space  between 
the  false  chords  and  sometimes  called  iho.  false  glottis; — one 
below,  the  space  between  the  true  chords,  called  the  g-lottis, 
and  leading-  into  the  lower  compartment;  and  one  on  either 
side,  being-  the  opening-  into  each  laryng-eal  pouch.  The  g-lot- 
tis  is  the  triang"ular  space  found  between  the  true  vocal  chords 
in  front  and  between  the  two  arytenoid  cartilag-es  behind. 

The  lower  compartment  is  simply  the  circular  space  enclosed 
by  the  cricoid  cartilag-e,  and  would,  therefore,  be  the  means  of 
establishing-  communication  between  the  Larynx,  above,  and 
the  Trachea,  below. 

Trachea. 

Succeeding-  the  larynx  comes  the  second  subdivision  of  the 
air  tube  known  as  the  trachea.  Commencing*  where  the  larynx 
terminates,  opposite  the  fifth  cervical  vertebra,  it  descends  in 
front  of  the  vertebral  column,  from  which  it  is  separated  by 
the  cesophag-us,  and  terminates  by  dividing-,  opposite  the  fifth 
dorsal  vertebra,  into  the  rig*ht  and  left  bronchi.  It  is  a  cylin- 
drical tube  flattened  on  its  posterior  aspect,  about  four  and  a 
half  inches  long-and  one  inch  in  diameter.  In  the  female  these 
dimensions  are  somewhat  less.  Its  appearance,  when  viewed 
from  the  front,  is  annulose,  due  to  the  fact  that  its  larg-est 
element  is  a  number — fifteen  to  twenty — -of  cartilag-inous 
ring-s,  one  lying-  above  the  other. 

The  flattening*  posteriorly  is  due  to  the  fact  that  each  ring-  is 
wanting-  in  its  posterior  third,  thus  leaving-  this  portion  of  the 
tracheal  wall  wanting-  in  cartilag-e.  The  ring-s  are  not  in  con- 
tact but  are  separated,  and  at  the  same  time  maintained  in 
position  by  a  fibro-clastic  membrane,  which  covers  both  sur- 
faces of  the  rings,  for  they,  in  fact,  lie  embedded  in  the  sub- 
stance of  the  membrane.   Between  the  posterior  extremities  of 


204  DESCRIPTIVE  ANATOMY. 

the  riug-s,  over  the  interval  left  by  their  imperfection,  the 
membrane  is  continued  and  is  here  strengthened  by  unstriated 
muscular  fibres,  both  long-itudinaland  transverse.  The  longi- 
tudinal are  unimportant;  but  the  transverse,  passing-  between 
the  posterior  extremities  of  the  rings,  can,  by  their  contraction, 
diminish  the  diameter  of  the  trachea. 

The  interior  of  the  trachea  is  lined  by  mucous  membrane, 
continuous  with  that  of  the  larynx  above  and  prolonged  below 
into  the  bronchi,  bronchial  tubes  and  ultimate  air  cells  of  the 
lungs.  Beneath  the  mucous  membrane,  between  it  and  the 
fibro-elastic  membrane,  is  a  yellow  elastic  membrane  which  is 
much  more  distinct  posteriorly,  where  the  fibres  which  com- 
pose it  are  gathered  into  longitudinal  bundles.  To  sum  up  its 
structure  we  say  the  trachea  is  lined  by  mucous  membrane, 
beneath  this  yellow  elastic  fibres,  external  to  this  a  yellow  fibro- 
elastic  membrane  lying  in  which  are  the  rings  of  the  trachea. 
Besides  these  there  are  transverse  muscular  fibres  between 
the  posterior  extremities  of  the  rings,  and,  scattered  around 
the  tube  some  unimportant  longitudinal  fibres. 

Bronchi. 

Taking  up  the  air  tube  again,  we  find  that  the  trachea,  or 
wind  pipe,  when  it  has  reached  a  point  corresponding  to  the 
front  of  the  fifth  dorsal  vertebra,  forks,  the  prongs  of  the  fork 
being  known  as  the  bronchi,  right  and  left.  Each  bronchus 
extends  from  its  origin  to  the  inner  surface  of  the  lung,  forming 
one  element  of  the  root  of  the  lung.  The  two  bronchi  are  not 
similar  and  the  difference  between  them  may  be  thus  stated: 
The  right  is  shorter,  larger  and  more  nearly  horizontal,  com- 
ing off  nearly  at  right  angles  to  the  trachea,  whereas  the  left 
has  a  considerable  obliquity  downward.  If  the  trachea  be  cut 
across  near  its  termination  and  the  cavity  examined,  a  slight 
antero-posterior  ridge  is  found  separating  the  two  bronchi. 
This  ridge  lies  nearer  the  left  than  the  right  side  and  in  con- 
sequence a  foreign  body  falling  into  the  trachea  is  more  likely 
to  enter  the  right  than  theleft  bronchus.  The  left  bronchus 
is  about  two  inches  long,  the  right  about  an  inch.  In  structure 
they  exactly  resemble  the  trachea. 


THE  VISCERA,  205 

Lungs. 

The  luno-s  are  a  pair  of  organs  found  in  the  thoracic  cavity, 
one  on  each  side  of  the  middle  line,  resting  upon  the  diaphram 
below  and  having-  the  heart  enclosed  in  the  pericardium,  lying" 
between  them.  Each  lung  is  conical  in  shape  with  its  base  be- 
low, resting  on  the  upper  surface  of  the  diaphragm  and  concave 
in  shape  to  correspond  with  that  surface.  The  apex  is  above 
and  extends  about  one  and  one-half  inches  into  the  root  of  the 
neck.  Besides  the  base  and  apex,  each  lung  presents  the  fol- 
lowing subdivisions:  the  posterior  border,  long,  thick  and 
rounded,  contrasting  strongly  with  the  anterior,  which  is  thin, 
short  and  sharp.  The  outer  surface  is  convex  to  correspond 
with  the  concave  inner  face  of  the  chest  wall.  The  inner  face, 
which  looks  towards  its  fellow,  is  marked  by  a  concavity  which 
is  caused  by  the  heart,  in  the  pericardium,  which  lies  between 
the  two  lungs.  The  inner  surface  of  the  left  lung  is  much 
more  concave  than  that  of  the  right,  owing  to  the  inclination 
of  the  heart  to  the  left.  A  little  above  and  posterior  to  the  cen- 
tre of  each  lung  on  its  inner  face  the  root  is  seen  to  enter  its 
substance.  The  root  is  made  up  of  various  elements,  nerves, 
lymphatics,  &c.,  but  its  chief  constituents  are  the  bronchus, 
pulmonary  artery  and  two  pulmonary  veins.  From  behind 
forward,  the  relation  which  these  structures  bear  to  one  another 
is  the  same  for  both  lungs,  viz:  Bronchus,  artery,  vein:  but 
from  above  downward  the  relation  is  different,  in  the  two  lungs. 
In  the  right  it  is  bronchus,  artery,  vein:  in  the  left,  artery, 
bronchus,  veins.  The  veins,  on  both  sides,  are  the  lowest, 
and  the  difference  is  caused  by  a  change  in  the  relation  of  the 
artery  and  bronchus  in  the  left  lung,  which  is  accounted  for 
b}'  the  downward  inclination  and  greater  length  of  the  left 
bronchus. 

Kach  lung  is  divided  by  fissures  into  lobes,  the  right  into 
three  and  the  left  into  two.  Commencing  about  three  inches 
from  the  apex,  on  the  posterior  border  of  each  lung,  an  oblique 
fissure  passes  through  the  lung  downward  and  forward  to  near 
the  lower  extremity  of  the  anterior  border.  In  the  right  lung 
there  is  another  fissure  which  begins  near  the  center  of  the  ob- 


206  DESCRIPTIVE  ANATOMY. 

lique  fissure  and  runs  nearly  horizontally  forward  to  the  ante- 
rior border,  thus  dividing-  the  rig-ht  lung-  into  three  lobes  known 
as  upper,  middle  and  lower.  In  the  left  lung  there  are  but  two 
lobes,  upper  and  low^er.  The  rig-ht  lung-  is  slig-htly  larg-er 
than  the  left,  ow^ng-  to  the  encroachment  of  the  heart  on  the 
left  lung-.  The  rig-ht,  how-ever,  is  shortened  by  the  rig-ht  lobe 
of  the  liver,  which  bulg-es  the  diaphrag-m  on  that  side,  and  the 
diif  erence  is  in  reality  not  g-reat — the  right  lung-  w^eig-hing  about 
twenty-tw^o  and  the  left  twenty  ounces. 

The  PleuraB. 

E^nveloping-  each  lung-  and  lining-  the  chest  w^all  is  a  serous 
membrane,  one  on  each  side. 

These  tw^o  membranes  are  the  two  pleurse.  They  are  sepa- 
rate from  each  other  and  each  forms  a  distinct  closed  sac  for 
its  lung-,  one  face  of  the  sack  lining  the  inner  surface  of  the 
chest  wall  while  the  other  completely  invests  the  lung.  In 
front,  behind  the  sternum,  the  two  pleura  approach  each  other 
closely,  and  are  sometimes  in  contact  about  the  centre  of  the 
sternum. 

In  tracing  the  reflections  of  the  pleura,  as  it  is  a  closed  sac, 
we  can  begin  at  any  point  and  following  it  around  will  return 
to  that  point.  Beginning  on  the  root  of  the  lung  we  trace  first 
the  visceral  layer,  or  pleura  pulmonalis,  and  then  the  parietal 
layer,  or  pleura  costalis,  the  two  being  continuous.  From 
the  front  of  the  root,  the  pleura  passes  forward  on  the  inner 
face  to  the  anterior  border  of  the  lung,  then  around  the  convex 
outer  surface  to  the  posterior  border  and  then  forward  on  the 
inner  face  to  the  back  of  the  root  of  the  lung  and  then  to  the 
side  of  the  vertebral  column,  where  it  becomes  the  parietal 
layer,  \vhich  passes  thence  along  the  inner  surface  of  the  chest 
wall  to  the  sternum  in  front,  where  it  leaves  the  chest  wall 
and  passes  backward  on  the  pericardium  to  the  front  of  the 
root  of  the  lung  to  become  continuous  with  the  visceral  layer 
which  we  have  just  traced.  The  free  surfaces  of  the  two 
layers  secrete  a  small  amount  of  liquid  which  renders  the 
movements  of  the  lungs  in  respiration  easy. 


THE  VISCERA.  207 


The  Mediastinum. 


Between  the  opposing-  surfaces  of  the  pleurae  and  the  sternum 
in  front  and  vertebral  column  behind,  there  is  a  space,  called 
the  mediastinum. 

This  space  is  of  ver}^  irreg-ular  shape,  varying-  in  size 
at  different  points.  It  is  conveniently  divided  into  the 
Superior,  Anterior,  Middle  and  Posterior.  The  Superior 
Mediastinum  extends  from  Sternum  to  vertebral  column  and 
is  all  that  portion  which  lies  above  the  level  of  the  pericardium, 
its  lower  boundary  being-  a  plane  extended  from  the  junction 
of  the  manubrium  and  g-ladiolus  in  front  to  the  lower  border 
of  the  fourth  dorsal  vertebra  behind.  On  either  side  would 
be  the  pleurae,  containing-  the  lung-s.  In  this  space  lie  the 
g-reat  vessels  spring-ing-  from  the  heart  and  the  aorta  and  the 
structures  passing  from  the  neck  into  the  Thorax. 

The  anterior  mediastium  is  bounded  in  front  by  the  sternum 
and  lower  costal  cartilag-es  of  the  true  ribs,  behind  by  the 
pericardium  and  on  either  side  by  the  pleura.  It  is  oblique 
in  direction,  from  above  downward  and  to  the  left  and  is  larger 
below  than  above. 

The  middle  niediasthuim  is  the  broadest  part  of  the  inter 
pleural  space  and  contains  the  heart  and  pericardium. 

The  -posterior  mediastinum  is  irregularly  triangular,  being 
bounded  in  front  by  the  pericardium  and  roots  of  the  lungs, 
behind  b}'  the  vertebral  column  and  laterally  b}'  the  pleural. 
It  extends  from  the  fourth  dorsal  vertebra  downward  and 
contains  many  important  cords. 

The  Heart. 

The  heart  is  a  hollow  muscular  organ  found  in  the  cavity  of 
the  chest,  13'ing  between  and  almost  surrounded  by  the  two 
lungs  ;  it  rests  upon  the  convex  upper  surface  of  the  diaphragm 
and  is  contained  in  the  middle  mediastinum.  It  is  contained 
in  a  closed  cavity,  formed  by  the  pericardium,  lying,  for  the 
greater  part  of  its  extent,  unattached  ;  but,  since  its  function 
is  the  maintenance  of  the  circulation  of  the  blood,  the  vessels 
which  bring  this  to  or  carry  it  from  the  heart  all  communicate 


208  DESCRIPTIVE  ANATOMY. 

with  its  upper  part  or  base,  and  thus  maintain  it  in  position. 
To  render  its  movements  free  in  the  pericardium,  that  struct- 
ure is  lined  by  a  serous  membrane  which,  like  all  others,  is  a 
closed  sac,  one  layer  lining-  the  pericardium  and  the  other  cov- 
ering- the  heart  from  the  orig-iu  of  the  vessels  on  one  side  to 
the  same  point  on  the  opposite  side.  The  portion  lining-  the 
pericardium  is  called  the  serous  pericardium  and  the  mem- 
brane which  it  lines  the  fibrous  pericardium.  The  heart 
is  conical  in  shape,  its  base  being  above  and  to  the  rig-ht 
and  its  apex  below  and  to  the  left.  It  is  about  five  inches 
long-,  three  and  a  half  inches  transversely  and  two  and 
a  half  antero  posteriorly.  Its  weig-ht  is  from  nine  to 
twelve  ounces,  varying-  in  the  two  sexes  and  being-  slig-htly 
larg-er  in  the  male. 

The  exact  position  of  the  heart  is  thus  stated  :  the  base  lies, 
behind  the  sternum,  corresponding-  to  a  line  drawn  between 
the  upper  borders  of  the  extremities  of  the  third  costal  carti- 
lag-es  ;  the  apex  is  downward  and  to  the  left,  striking-  the  chest 
wall  at  the  space  between  the  fifth  and  sixth  ribs,  three  to 
three  and  one-half  inches  to  the  left  of  the  middle  line,  about 
opposite  the  g-ladio-xiphoid  joint. 

The  cavity  of  the  heart  is  separated  into  a  venous  and  an 
arterial  half,  or  apartment,  by  an  obliquely  vertical  septum, 
which  cuts  off  all  communication  between  the  halves.  The  posi- 
tion of  this  septum  can  be  predicted  by  an  inspection  of  the 
exterior  of  the  heart,  for  it  is  marked  by  a  g-roove  passing-  from 
the  base  anteriorly  and  to  the  left  downward  to  the  rig-ht  of 
the  apex  to  run  along-  the  posterior  aspect  of  the  heart  and 
terminate  at  the  base,  towards  its  rig-ht  aspect.  An  artery  is 
found  lying-  in  this  g-roove,  which  is  called,  for  a  reason  here- 
after g-iveu,  interventricular.  From  the  position  of  the  g-roove 
it  is  seen  that  the  apex  of  the  heart  is  formed  entirely  by  the 
left  half,  the  front  of  the  heart  mainly  by  the  rig-ht  half,  while 
the  back  is  the  product,  principally,  of  the  left  half. 

When  the  heart  is  laid  open  its  entire  cavity  is  seen  to  be 
lined  by  a  serous  membrane,  continued  into  the  vessels  which 
communicate  with  it  called  the    endocardium,   and  that  each 


THE  VISCERA.  209 

lateral  half  is  subdivided  by  a  partial  horizontal  septum  into 
two  cavities,  the  upper  called  the  auricle,  rig-ht  or  venous,  and 
left,  or  arterial,  the  lower,  the  ventricle,  rig-ht,  or  venous  and 
left,  or  arterial. 

The  position  of  the  horizontal  septum  is  indicated  by  a 
groove  passing"  around  the  heart  called  the  auriculo-ventricu- 
lar. 

In  the  adult  the  venous  blood  of  the  entire  body,  with  the  ex- 
ception of  that  of  the  heart  itself,  is  returned  into  the  venous 
auricle  by  two  g-reat  veins  called  vena^  cavas,  superior  and 
inferior,  the  one  bringing-  the  blood  from  the  head  and  upper 
extremities,  the  other  from  the  lower  extremities  and  bod}^ 
The  venous  blood  from  the  heart  is  returned  to  the  venous 
auricle  by  a  separate  vein  called  the  coronary,  which,  just  as 
it  is  about  to  enter  the  auricle,  dilates  into  what  is  known  as 
the  coronary  sinus.  Besides  these  channels  for  the  return  of 
the  venous  blood,  there  exist  numerous  minute  apertures  in 
every  cavity  of  the  heart  throug"h  which  its  venous  blood  may 
enter  to  a  small  extent.  These  are  called  foramina  Thebesii. 
The  venous  blood  thus  collected  by  the  venous  auricle  is  driven 
bv  its  pulsation  into  the  venous  ventricle,  with  which  it  com- 
municates by  an  aperture  througfh  the  horizontal  septum  called 
the  venous  auriculo-ventricular  opening".  From  the  venous 
ventricle  the  blood  is  sent  into  the  pulmonary  artery  which 
soon  divides  into  a  branch  to  each  lung*. 

Taking-  up  the  appearances  seen  in  the  cavities  of  the  heart, 
we  beg-in  with  the  venous  auricle. 

The  venous  miricle  consists  of  two  portions;  the  larg-er  part 
is  called  the  sinus,  but,  communicating-  with  this  and  project- 
ing- forward,  is  an  ear  shaped  addition,  called  the  appendix 
auricula; — hence  the  name  of  the  auricles.  The  sinus  of  the 
venous  auricle  presents  the  following- objects:  At  its  upper  back' 
part,  the  opening-  of  the  superior  vena  cava;  at  the  lower  back 
part,  the  opening-  of  the  inferior  vena  cava ;  between  the 
two  opening's  a  slig-ht  thickening-  of  the  auricular  wall  called 
the  tubercle  of  Lower  ;  between  the  opening-  for  the  inferior 
vena  cava  and  the  auriculo-ventricular   opening-  is  the  opening- 

Des  Anat — 14 


210       ~  DESCRIPTIVE  ANATOMY. 

for  the  coronary  sinus,  g-uarded  by  a  valve-like  fold  of  endo- 
cardium called  the  coronary  valve;  on  the  septum  between  the 
two  auricles,  an  oval  depression,  called  the  fossa  ovalis,  and 
surrounding-  this,  except  below,  a  ridg^e  called  annulus  ovalis; 
extending-  along-  the  wall  of  the  auricle  from  the  opening-  of 
the  inferior  vena  cava  to  the  fossa  ovalis,  is  a  ridg-e,  the  remains 
of  the  Eustachian  valve  of  the  foetus;  the  lining-  membrane 
presents  ridg-es  caused  by  little  muscular  columns  called 
musculi  pectinati;  the  opening-  throug-h  the  horizontal  septum 
into  the  venous  ventricle,  and,  lastly,  foramia  Thebesii. 

To  sum  up  we  have  the  following-:  1st,  superior  vena  cava  ; 
2d,  inferior  vena  cava;  3d,  coronary  sinus  ;  4th,  foramina  The- 
besii; 5th,  venous  auriculo- ventricular  ;  and  six  other  appear- 
ances, viz:  1st,  musculi  pectinati  ;  2nd,  tubercle  of  Lower  ; 
3d,  coronary  valve  ;  4th  I^^ustachian  valve  ;  5th,  fossa  ovalis  ; 
6th,  annulus  ovalis. 

The  venous  ventricle  has  two  opening-s  communicating-  with 
it,  one  for  the  pulmonary  artery  and  the  other  from  the  venous 
auricle.  The  venous  auriculo- ventricular  opening  is  surrounded 
by  an  oval,  fibrous  ring-  to  which  the  seg-ments  of  the  valve 
are  attached.  To  prevent  regurg-itation  of  blood  when  the 
ventricle  contracts,  the  opening-  is  guarded  by  a  valve  consist- 
ing- of  three  flaps,  formed  of  folds  of  endocardium  strength- 
ened by  fibrous  tissue  and  some  muscular  fibres,  which  are 
triangular  in  shape  with  the  base  attached  to  the  fibrous  ring 
and  the  apex  free.  When  the  ventricle  contracts,  the  blood 
insinuates  itself  behind  these  flaps,  which  when  the  ventricle 
is  passive,  hang  loosely  in  its  cavity,  and  forces  them  before 
it  until  they  come  together,  their  apices  meeting  in  the  centre 
of  the  opening.  The  segments,  which  are  quite  flexible,  are 
kept  from  being  forced  into  the  auricle  by  the  attachment  of  a 
number  of  muscular  and  tendinous  cords  which  hold  them  in 
the  ventricle.  The  muscular  columns  are  called  columnse 
carnese  and  are  divided  into  three  sets  arranged  as  foUow^s  : 
some  form  mere  ridges,  being  attached  to  the  wall  of  the  ventricle 
throughout  their  length;  the  second  set  are  attached  to  the  wall' 
of  the  ventricle  by  each  end  and  are  free  in  the  middle;  while 
the  third  are  attached  by  one  end  only  to  the   ventricular  wall, 


THE  VISCERA.  211 

terminatingf  at  the  other  in  tendinous  cords  which  are  them- 
selves attached  to  the  ventricular  aspect  of  the  segments  of 
the  valve  and  are  only  long-  enouo-h  to  allow  these  to  close  with- 
out floatino-  into  the  auricle.  The  valve  thus  formed  is  known 
as  the  tricuspid,  and  the  tendinous  cords  as  chordae  tendineae. 

The  blood,  driven  by  the  contraction  of  the  venous  ventricle, 
is  forced  into  the  pulmonary  artery  and,  when  the  ventricle 
ceases  to  contract,  would  aofain  return  to  it  were  it  not  for  a 
valvular  arrang-ement  here,  called  the  pulmonary  semilunar 
valve,  which  guards  the  orifice  of  the  pulmonar}"  artery.  The 
semilunar  valve  is  three  segments  arranged  around  the  interior 
of  the  pulmonary  artery,  just  at  its  commencement.  Each 
segment  is  semilunar  in  shape,  its  convex  border  being  at- 
tached w^hile  the  superior  border  is  free  and  straight.  They 
consist  of  folds  of  lining  membrane,  strengthened  b}'^  fibrous 
tissue  which,  just  at  the  centre  of  the  free  edge,  is  aggregated 
into  a  projection  called  corpus-arantii.  In  the  centre  the  valve 
lacks  fibrous  tissue  and  presents  a  lunated  space.  Behind 
each  segment  there  is  a  depression  caused  by  a  dilation  of 
the  artery,  called  sinus  of  Valsalva,  and  when  the  ventricle 
ceases  to  contract  the  blood,  seeking  to  re-enter  the  cavity, 
enters  the  sinuses  of  Valsalva  and  forces  the  segments  together 
until  they  meet  along  their  free  edges  and  close  the  orifice. 
The  corpora  arantii  have  small  effect  in  closing  this  orifice. 

The  objects  seen  in  the  right  ventricle  then  are :  1st,  col- 
umnar carnear;  2d,  chordae  tendineae;  3d,  venous  auriculo-ven- 
tricular  opening;  4th,  opening  into  pulmonary  artery;  5th,  tri- 
cuspid valve;  6th,  semilunar  valve;  7th,  foramina  Thebesii. 

The  arterial  auricle  has  thicker  walls  than  the  venous,  be- 
ing about  one-eighth  inch  thick  while  the  right  is  only  one- 
twelfth  inch.  It  presents  musculi  pectinati,  which  are  fewer 
in  number  than  in  the  right  auricle,  being  almost  confined  to 
the  appendix  auricula;;  the  arterial  auriculo-ventricular  open- 
ing; the  openings  for  the  four  pulmonary  veins,  which  return 
the  blood  from  the  lungs.  Two  of  these  veins  come  from  each 
lung,  the  two  from  the  left  sometimes  uniting  before  entering 
the  auricle. 


212  DESCRIPTIVE  ANATOMY. 

To  sum  up,  we  have  1st  opening's  for  four  pulmonary  veins, 
2nd  arterial  auriculo-ventricular  opening,  3rd  musculi  pectinati. 

The  arterial  ventricle  has  walls  three  times  as  thick  as  those 
of  the  venous,  being-  seven  lines  thick  while  the  venous  is  only 
about  two  and  a  half  lines.     The  left  side  of  the  heart,  there- 
fore, is  much  more  powerful  than  the  right;  this  being  due  to 
the  fact  that  while  the  venous  ventricle  has  only  to  drive  the 
blood  into  the  lungs,   the  arterial  has  to  send  it  throughout 
the  entire  system.     On  the  walls  of  the  arterial  ventricle  are 
seen  columns  carneae  much  more  prominent  and  more  intimate- 
ly intersecting  than  in  the  venous  ventricle,  but  similar  to  them 
in  arrangement,  viz   :  some  attached   throughout  their  length, 
some  at  each  end  and  free  in  the  middle,  some  attached  at  one 
end  to  the  wall  of  the  ventricle,  while  the  others  terminate  in 
tendinous  cords  attached  to  the  ventricular  aspect  of  the  bicuspid 
valve.     The  blood  is  forced  from  the  arterial  auricle  into  the 
arterial  ventricle,  and  when  this  contracts  it  is  forced  into  the 
aorta.      Both  these  openings  are  guarded   by  valves.      The 
valve   guarding   the   arterial  auriculo-ventricular  opening   is 
known  as  the  bicuspid,  or  mitral,  and  is  arranged  upon  the  same 
principle  as  the  tricuspid,  being  made  up  of  two   segments  at- 
tached by  their  bases  to  the  fibrous  ring  around  the   opening 
while  their  apices  are  free  in  the  cavity  of  the  ventricle.      It 
consists  of  folds  of  endocardium  strengthened  by  fibrous  and 
muscular  tissue  and  receives    the  attachment  of  the  chorda? 
tending.     It  differs  from  the  tricuspid  valve  in  being  stronger 
and    in  having   only  two  segments.       The  opening  into  the 
aorta  is  guarded   by  the  aortic  semiluna  valve,    which  is  in 
every  way  the  counterpart  of  the  pulmonary  semilunar^  except 
in  being  larger  and  stronger,  consist  of   three   segments  of 
lining   membrane   and   fibrous    tissue,    with    corpora-arantii, 
lunated  spaces  and   sinuses  of  Valsalva.     The  mechanism  of 
their  action  is    also  the  same  as  in  the  pulmonary  semilunar. 

To  sum  up,  there  are  in  the  arterial  ventricle:  1st,  columnae, 
earner;  2d,  chords  tendineae;  3d,  arterial  auriculo-ventricular 
opening;    4th,  aortic  opening;  5th,  bicuspid  valve;  6th,  aortic 
semilunar  valve. 


THE  MUSCULAR  SYSTEM.  213 


THE  MUSCULAR  SYSTEM. 

When  an  incission  is  made  in  any  part  of  the  body,  the 
following-  structures,  from  without  inward,  are  met  with:  1st, 
ski)i\  2d,  superficial  areolar  fascia  whose  existence  allows  the 
free  movement  observed  in  almost  every  part  of  the  integ-ument. 
It  consists  of  two  layers,  betw^een  which  is  g-enerally  found 
fatty  tissue,  varying- in  quantity  indifferent  parts  of  the  body; 
3d,  beneath  the  superficial  fascia,  in  some  parts  of  the  body, 
are  found  the  muscles  with  their  proper  i?ivesti?ijy-/ascia;  while 
in  others  there  is  interposed  between  them  and  the  superficial 
fascia  a  strong,  and  more  or  less  thick,  membrane,  called  the 
investing  fascia,  or  deep  fascia  which  frequently  g-ives  off 
from  its  deep  face  partitions,  which  separate  different  g-roups 
of  muscles. 

The  function  of  muscles  is  to  produce  movement,  most  of 
them  being  attached  to  bone,  some  havin^r  no  bony  attach- 
ment, while  others  are  attached  to  bone  by  one  extremity  the 
other  terminating  in  some  soft  tissue.  When  a  muscle  is 
attached  to  bone  by  both  extremities  a  movable  joint  is  almost 
invariably  found  between  the  two  extremities,  otherwise  no 
movement  would  occur  when  the  muscle  attempted  to  contract, 
so  that,  as  a  rule,  those  muscles,  which  lay  hold  of  bone  at 
at  both  extremities,  are  attached  to  different  bones  at  either 
end.  The  two  attachments  of  a  muscle  are  spoken  of,  one  as 
the  nrii^in,  the  other  as  the  insertion,  the  orig-in  being-  usually 
that  attachment  susceptible  of  the  least  motion,  and  as  a  rule, 
especially  true  of  the  limbs,  the  orig-in  is  the  point  nearest  the 
body,  or  the  mid-line  of  the  body.  The  action  of  a  muscle  con- 
sists in  the  shortening  of  its  leng-th,  thus  drawing  the  parts 
to  which  it  is  attached  nearer,  usually  by  movement  of  the 
part  into  which  it  is  inserted.  Some  movements  are  two  com- 
plex to  be  brougfht  about  by  one  muscle  and  result  from  the 
co-ordinated  action  of  several. 

The  striated  muscles  are  the  red,  fleshy  portion  of  the  body, 
though   g-enerally  a  muscle   consists   of    two   parts  :  the    red 


214  DESCRIPTIVE  ANATOMY. 

fibres,  g-athered  into  bundles,  fasciculi,  forming-  a  coarse,  or  a 
fine  muscle,  and  a  white,  toug-her,  strong-er  portion  called  its 
tendon.  With  few  exceptions  the  tendon  is  found  at  the  ex- 
tremities of  the  muscle,  and,  as  it  is  so  much  strong-er,  bulk 
for  bulk,  the  tendon  is  much  the  smaller  part  of  the  muscle, 
thus  economizing-  space  at  the  attachments.  The  portion  of 
muscle  between  its  tendons  of  orig-in  and  insertion  is  called 
the  belly  of  the  muscle.  In  a  few  instances  a  muscle  has  two 
bellies,  since  it  may  have  a  central  tendon. 

The  names  of  most  muscles  are  derived  from  one  of  the 
following-  facts  :  1st,  the  position  which  it  occupies  ;  2nd,  its 
shape ;  3rd,  the  direction  of  its  fibres  ;  4th,  its  attachments  ; 
5th,  its  action  ;  6th,  the  number  of  its  points  of  orig-in. 

The  Abdominal  Muscles. 

The  anterior  abdominal  wall  is  formed  chiefly  by  six  flat, 
thin  muscles,  three  on  each  side  of  the  middle  line,  called  the 
broad  muscles  of  the  abdomen.  Besides  these  there  are  two 
other  pairs,  the  pyramidales,  small  and  insig-nificant,  and  the 
recti  which  are  long-  and  narrow.  The  abdominal  wall  con- 
sists of  the  following  structures  from  without  inward,  viz  : 
1st,  integ-ument ;  2d,  two  layers  of  superficial  fascia  with  fatty 
tissue  interposed  ;  3d,  the  external  oblique  muscle  ;  4th,  the 
internal  oblique  ;  5th,  the  transversalis  ;  6th,  the  transversalis 
fascia;  7th,  the  parietal  layer  of  peritoneum.  These  muscles 
all  terminate  in  tendinous  fibres  as  they  approach  the  median 
line  ;  and,  since  there  is  no  bone  for  them  to  seize,  their  fibres 
interlock,  forming-  a  white  line  extending-  from  the  ensiform 
cartilag-e  to  the  symphysis  pubis  called  the  linea  alba.  The 
whole  line  is  sunken  below  the  surrounding-  surface  and 
presents  about  its  centre  the  umbilicus  or  navel.  The  sunken 
appearance  is  caused  by  the  bulging-  of  the  recti,  which  lie  on 
either  side  of  it,  the  width  of  the  linea  alba  corresponding  to 
the  interval  between  the  recti. 

External  Oblique. 

The  external  oblique  of  the  abdomen  derives  its  name  from 
the  downward  and  inward  direction  of  its  fibres  and  from  its 


THE  MUSCULAR  SYSTEM.  215 

position,  being-  external  to  another  oblique  muscle.  It  arises 
by  eig-ht  flesiiy,  tooth-like  processes  or  digitations  from  the 
anterior  surfaces  of  the  eight  lower  ribs.  The  upper  five 
digitations  interlock  with  similar  processes  of  the  serratus 
magnus,  the  lower  three  with  the  latissimns  dorsi.  From 
their  origin  the  fibres  pass  downward  and  inward,  the  dig-ita- 
tions  gradually  blending  to  form  the  belly  of  the  muscle  which, 
toward  the  front  of  the  abdomen,  terminates  in  a  thin,  flat 
tendon,  called  an  aponeurosis,  which  is  inserted  into  the  linea 
alba  from  the  sternum  to  the  symphysis  pubis.  The  posterior 
fibres  pass  almost  vertically  downward  and  are  inserted  into 
about  the  anterior  one-half  or  two-thirds  of  the  outer  lip  of  the 
crest  of  the  ilium  ;  while  the  intermediate  fibres  are  inserted 
into  the  anterior  superior  spinous  process  of  the  ilium  and  into 
the  spine  and-  pectineal  line  of  the  pubes.  That  portion  of  the 
aponeurosis  which  extends  from  the  anterior  superior  spinous 
process  of  the  ilium  to  the  spine  of  the  pubes  is  called  Poiiparf  s 
ligament.  It  is  the  lower  border  of  the  aponeurosis,  is  free 
between  its  points  of  attachment  and  folded  slightly  inward  on 
itself.  About  an  inch  from  the  spine  of  the  pubes  Poupart's 
ligament  sends  downward  some  fibres  which  are  inserted  into 
the  pectineal  line  of  the  pubis,  forming  Gimberuar s  lig-ameut, 
which  is  triangular  in  shape  with  its  apex  within  and  its  base 
extending  for  about  an  inch  outward. 

At  the  lower,  inner  part  of  the  aponeurosis  is  seen  an  open- 
ing, near  the  symphysis  pubis,  called  the  external  abdominal 
ring.  It  is  formed  b}^  a  separation  of  the  fibres  of  the  aponeu- 
rosis, is  triangular  in  shape  and  oblique  in  direction,  its  apex 
being  upward  and  outward  and  its  base  downward  and  inward 
at  the  crest  of  the  pubes.  The  edges  of  the  aponeurosis  which 
form  the  sides  of  the  ring  are  called  its  pillars,  internal  and 
external,  the  external  being  inserted  into  the  spine  of  the 
pubes  and  the  internal  interlocking  with  the  internal  pillar  of 
the  opposite  side  over  the  front  of  the  pubes.  For  a  short 
distance  the  apex  of  the  ring  is  obscured  by  some  curved 
fibres  called  intercolumnar  fibres.  The  external  abdominal 
ring  transmits  in  the  male  the  spermitic  cord  and  in  the  female 
the  round  licfament. 


216  DESCRIPTIVE  ANATONY. 

Internal  Oblique. 

The  internal  oblique  muscle  of  the  abdomen  derives  its  name 
from  the  upward  and  inward  obliquity  of  its  fibres  and  from 
the  position  it  occupies  just  beneath  the  external  oblique.  It 
arises  by  a  thin  tendinous  membrane,  called  the  fascia  lumbo- 
rum,  from  the  spinous  processes  of  the  lumbar  vertebrae,  the 
anterior  two-inirds  of  the  middle  lip  of  the  crest  of  the  ilium, 
and  from  the  outer  half  of  Poupart's  lig"ament. 

The  fascia  lumborum  terminates  in  fleshy  fibres  on  the  side 
of  the  abdomen,  and  those  fibres  spring-ing-  from  the  crest  of 
the  ilium  are  also  fleshy:  these  radiate  somewhat,  the  general 
direction,  however,  being  upward  and  inward,  and  are  inserted, 
posteriorly,  into  the  cartilages  of  the  four  lower  ribs;  while 
on  the  front  of  the  abdomen  the  fibres  become  aponeurotic  and 
are  inserted  into  the  whole  length  of  the  linea  alba.  The  fleshy 
fibres  which  rise  from  the  outer  half  of  Poupart's  ligament 
are  blended  with  fibres  of  the  transversalis  which  arise  from 
the  same  part  of  the  ligament.  These  blended  fibres  arch  down- 
ward and  inward  and  form,  so  long  as  they  remain  fleshy,  the 
conjoined  arch;  but  as  they  descend  they  become  tendinous, 
forming  the  conjoined  tendon  which  is  inserted  into  the  crest 
and  pectineal  line  of  the  pubes.  By  reason  of  the  arched 
direction  of  these  fibres  there  is  a  short  space  between  them 
above  and  Poupart's  ligament  below,  their  conjoined  arch 
without  and  conjoined  tendon  within,  where  the  wall  of  the 
abdomen  has  but  one  muscular  element,  viz:  the  aponeurosis 
of  the  external  oblique.  If  an  incision  were  made  at  this  point 
we  would  pass  through:  1st,  the  integument;  2d.,  two  layers 
superficial  fascia  ;  3d,  the  aponeurosis  of  the  external  oblique; 
4th,  transversalis  fascia  and  the  parietal  layer  of  the  perito- 
neum. The  conjoined  tendon  descends  just  behind  the  external 
abdominal  ring,  so  that  at  this  point  the  wall  is  wanting  in 
only  one  muscular  element — the  aponeurosis  of  the  external 
oblique. 

Transversalis. 

The  transversalis  derives  its  name  -from  the  horizontal 
direction  of  its  fibres.     It  lies  just  beneath  the  internal  oblique 


THE  MUSCULAR  SYSTEM.  217 

and  is  the  deepest  of  the  three  broad  muscles  of  the  abdomen. 
It  arises  by  means  of  an  aponeurosis  trom  the  transverse  and 
spinous  processes  of  the  lumbar  vertebrae,  fleshy  from  the  inner 
aspect  of  the  cartilag-es  of  the  six  inferior  ribs,  interlocking- 
with  the  diaphragm,  fleshy  from  the  anterior  two-thirds 
of  the  inner  lip  of  the  crest  of  the  ilium  and  fleshy  from 
somewhat  less  than  the  upper  half  of  Poupart's  lio-ament. 
The  posterior  aponeurosis  becomes  fleshy  on  the  side  of  the 
abdomen  and  these  fibres,  being-  reinforced  by  those  which 
arise  from  the  costal  cartilag-es  and  crest  of  the  ilium,  pass 
forward,  become  aponeurotic  and  are  inserted  into  the  whole 
leng-thof  the  linea  alba.  The  fibres  which  rise  from  Poupart's 
ligament  blend  with  those  of  the  internal  oblique  to  form  the 
conjoined  arch  and  conjoined  tendon  which  is  inserted  into  the 
crest  and  pectineal  line  of  the  pubes. 

Rectus. 

The  rectus  abdominis  derives  its  name  from  the  straig-ht 
course  of  its  fibres.  It  lies  on  the  front  of  the  abdomen, 
beside  the  linea  alba,  surrounded  by  the  aponeuroses  of  the 
three  broad  muscles  of  the  abdomen.  It  is  flat  and  ribbon-like 
in  shape.  It  arises  by  a  flat  tendon  from  the  front  of  the 
symphysis  pubis  and  crest  of  the  pubes  ;  as  it  ascends  it 
becomes  fleshy  and  broader  and  terminates  by  three  digitations 
which  are  inserted  into  the  fifth,  sixth  and  seventh  cartilag-es 
just  beside  the  sternum.  In  the  upper  half  of  its  course  the 
rectus  presents  three  or  four  tendinous  intersections  which  are 
called  linear  transversaj.  Before  the  aponeurosis  of  the  exter- 
nal oblique  has  been  removed,  the  outer  edg-e  of  the  rectus 
presents  a  curved  ridg-e  called  linea  semilunaris. 

The  rectus  as  it  ascends  is  enclosed  between  the  aponeu- 
roses of  the  three  broad  muscles,  and  these  form  what 
is  called  its  sheath.  This  sheath  is  complete  in  front 
for  the  whole  leng-th  of  the  muscle,  but  behind  is 
v.-anting-  for  its  lower  fourth.  It  is  thus  formed:  for 
the  upper  three-fourths  of  the  rectus,  or  from  a  point  half 
way  between  the  umbilicus  and  the  symphysis  pubis  upward 
to  its  insertion,  the  rectus  has  in  front  the  aponeurosis  of  the 


218  DESCRIPTIVE  ANATOMY. 

external  oblique  and  half  the  aponeurosis  of  the  internal 
oblique  ;  while  for  the  same  distance  behind  it  has  the  aponeu- 
rosis of  the  transversalis  and  half  of  the  aponeurosis  of  the 
internal  oblique,  the  latter  aponeurosis  splitting,,  when  it 
reaches  the  outer  edge  of  the  rectus,  sending  one  layer  in 
front  and  the  other  behind  that  muscle.  Of  course  it  also  has 
behind  it  the  transversalis  fascia  and  the  parietal  layer  of 
peritoneum  separating  it  from  the  abdominal  cavity.  For  its 
lower  fourth,  that  is  from  the  point  midway  between  the  um- 
bilicus and  symphysis  pubis,  all  three  aponeuroses  pass  in  front 
of  it ;  and  behind  it  is  separated  from  the  abdominal  cavity 
only  by  the  parietal  layer  of  the  peritoneum  and  the  transver- 
salis fascia.  Where  the  sheath  ends  behind  it  is  curved  and  is 
called  the  fold  of  Douglas. 

Fyramidalis. 

The  -pyramidalis  abdominis  is  small  and  derives  its  name 
from  its  pyramidal  shape.  It  is  found  in  the  sheath  of  the 
rectus,  in  front  of  its  lower  portion,  and  is  frequently  absent 
on  one  or  both  sides.  It  rises  from  the  front  of  the  crest  of 
the  pubes  and  passes  upward,  tapering  as  it  ascends  to  be  in- 
serted into  the  linea  alba  half  way  to  the  umbilicus. 

Action — The  abdominal  muscles  are  agents  of  expulsion  as 
in  voiding  the  urine  and  faeces  and  in  terminating  labor.  They 
are  also  agents  of  forced  expiration,  for  when  they  contract 
they  diminish  the  size  of  the  abdominal  cavity,  forcing  the 
abdominal  viscera  against  the  walls  of  that  cavity  and  thus 
driving  the  diaphragm  upward,  while  at  the  same  time,  by 
drawing  down  the  ribs,  they  in  a  measure  diminish  the  size  of 
the  thorax. 

They  can  also,  acting  from  below,  flex  the  body  on  the 
pelvis;  or,  acting  from  above,  draw  the  pelvis  and  lower  ex- 
tremities upward  on  the  body.  One  External  oblique,  acting 
alone,  would  draw  the  body  downward  and  to  the  side  opposite 
the  muscle  acting.  Of  course,  if  the  fixed  point  be  above,  it 
would  draw  the  pelvis  upward  and  towards  the  muscle  which 
is  acting.  The  internal  obliquo.  of  one  side  may  act  in  concert 
with  the  external  oblique  of  the  opposite  side.     The  tra?is- 


THE  MUSCULAR  SYSTEM.  219 

i'e7'sales,  acting-  together,  compress  the  abdominal  contents 
backward  and  inward.  The  }-ecti,  w^hen  the  lower  attachment 
is  fixed, draw  the  body  downward;  or,  w^hen  acting- from  above, 
will  draw^  the  pelvis  upward.  The  fyramidales  are  tensors  of 
the  linea  alba. 

These  muscles  are  supplied  by  the  lower  intercostal  nerves 
and  the  ilio-hypog-astric.  Blood  is  received  from  the  lumbar 
low^er  intercostal,  deep  epig^astric  and  internal  mamuary. 

Diaphragm. 

1st.  Definition  and  position — The  diaphrag-m  is  the  arched 
muscular  septum  between  the  tw^o  cavities  of  the  trunk,  pre- 
senting- its  upper  convex  surface  as  the  floor  of  the  thorax  and 
its  equally  concave  under  surface  as  the  roof  of  the  abdomen. 

2nd.  Relations — By  its  upper  surface  it  supports  the  pleura 
on  either  side,  containing*  the  lungs,  and  the  pericardium  in 
the  centre,  containing  the  heart.  Below  it  is  covered  by  per- 
itoneum and  is  in  relation  with  the  liver,  spleen,  stomach, 
pancreas  and  kidneys. 

3rd.  Origin — In  front  it  arises  from  the  posterior  surface 
of  the  sternum,  on  each  side  from  the  inner  surface  of  the  six 
lower  ribs  and  from  a  ligamentum  arcuatum  externum  and 
internum,  behind  from  the  front  of  the  vertebral  column  by 
two  crura. 

4th.   Its  points  of  origin  studied  individually. 

{a)  Between  that  part  which  arises  from  the  posterior  sur- 
face of  the  sternum  and  that  part  on  each  side  which  arises 
from  the  adjacent  ribs  there  usually  exists  a  fissure  for  a  short 
distance,  the  muscular  structure  here  being  wanting,  the 
aperture,  which  would  otherwise  exist,  between  the  thoracic 
and  abdominal  cavities  being  closed  by  other  structures. 

ib)  The  origin  from  the  inner  surface  of  the  ribs  is  by  digi- 
tations  which  interlock  with  similar  digitations  of  the  transvcr- 
sulis  abdominis. 

{c)  The  lig-ameiitum  arcualum  cxIcdiudi  arches  across  the 
quadratus  lumborum  muscle  from  the  apex  of  the  twelfth  rib 
to  the  apex  of  the  transverse  process  of  the  first  or  second 
lumbar  vertebra,  usually  the  second. 


220  DESCRIPTIVE  ANATOMY. 

{d)  The  ligamentuni  arcuatum  internum  arches  over  the 
psoas  magnus  muscle  from  the  apex  of  the  transverse  process 
of  the  first  or  second  lumbar  vertebra  to  be  lost  in  the  crus  of 
the  same  side. 

{e)  The  rig-ht  crus  arises  tendinous  from  the  front  of  the 
bodies  of  the  second,  third  and  fourth  lumbar  vertebra. 

{/)  The  left  crus  arises  tendinous  from  the  front  of  the  bod- 
ies of  the  second  and  third  lumbar  vertebse.  It  is  smaller  as 
well  as  shorter  than  the  rig-ht. 

5th.   The  appearances  which  it  presents. 

The  muscular  fibres  of  the  diaphragm,  as  they  are  making- 
for  the  centre,  become  tendinous.  The  central  portion,  there- 
fore, is  called  the  tendinous  portion  and  is  arrang-ed  like  a 
clover  leaf,  presenting  a  central,  a  rig-ht  and  a  left  leaflet,  the 
tendon  is  therefore  called  trefoil  or  central  tendon. 

The  diaphragm  is  pierced  by  three  large  apertures  which 
are  for  the  transmission  of  the  following  structures,  viz:  1st, 
descending-  aorta ^  vena  azyg-os  major,  thoracic  duct  and  some- 
times the  sympathetic  nerve\  2d,  the  ascending  vena  cava;  3d, 
(jesophag'us  "ajoA  ^neinnog-astric  nerves. 

The  crura,  as  stated,  arise  tendinous  from  the  front  of  the 
vertebral  column,  but  as  they  ascend  they  become  fleshy  and 
leave  a  slight  interval  between  them.  Over  the  front  of  the 
twelfth  dorsal  vertebrae  each  crus  gives  off  from  its  inner  side 
a  bundle  of  fibres  which  crosses  obliquely  to  join  the  oppo- 
site crus,  the  one  from  the  right  crus  being  usually  in  front. 
This  interchange  of  fibres  is  known  as  the  decussation  of  the 
crura  and  it  leaves  between  its  commencement  and  the  verte- 
bral column  an  opening  which  is  known  as  the  aortic.  This 
opening  is  over  the  front  of  the  bod}^  of  the  twelfth  dorsal 
vertebra,  generally  slightly  to  the  left  of  the  middle  line,  but 
sometimes  on  it.  The  opening  is  behind  the  diaphragm  and 
not  through  it. 

The  decussating  fibres,  after  passing  into  the  opposite  crus, 
again  separate  from  each  other  leaving  an  opening  around 
which  thej^  again  unite.     This  is  the  oesophageal  opening  and 


THE  MUSCULAR  SYSTEM.  221 

is  situated  above  and  to  the  left  of  the  aortic  opening-,  between 
it  and  the  middle  leaflet,  and  about  opposite  the  tenth  dorsal 
vertebra. 

The  opening-  for  the  inferior  vena  cava  is  to  the  rig-ht  of  the 
middle  line,  between  the  rig-ht  and  middle  leaflets  of  the  ten- 
dinous centre  and  about  opposite  the  ninth  dorsal  vertebra. 

6th.  Action — The  diaphrag-m  is  a  respiratory  muscle  and  an 
ag-ent  of  expulsion.  When  it  contracts,  as  it  does  eig"hteen  to 
twenty  times  a  minute,  it  descends,  becoming-  less  arched  and 
thus  increasing-  the  size  of  the  thorax  while  it  decreases  the 
size  of  the  abdomen,  thoug-h  the  latter  is  compensated  by  the 
bulg-ing-  of  the  anterior  abdominal  walls;  but  should  it  be  neces- 
sary to  exert  a  straining-  effort,  as  in  voiding-  the  urine  or  faeces 
or  in  parturition,  the  muscles  of  the  abdominal  wall  contract 
at  the  same  time  that  the  diaphragm  does,  so  that  the  abdominal 
cavity  is  diminished  in  size  from  above  downward  as  well  as 
from  before  backward,  and  its  viscera  subjected  to  compres- 
sion. When  the  diaphram  relaxes  it  ag-ain  ascends,  thus  lessen- 
ing- the  size  of  the  thoracic  cavity. 

The  diaphrag-m  is  supplied  by  the  phrenic  nerves.  Blood 
vessels  come  from  the  internal  mammary  and  the  phrenic 
branches  of  the  abdominal  aorta. 

ftuadratus  Lumborum. 

The  quadratus  lumborum  is  a  quadrilateral  muscle  found  in 

^he  posterior  abdominal  wall,  in  the  lumbar  reg-ion  lying-  beside 

:he  vertebral  column.     It  is  enclosed  between  the  middle  and 

anterior   lamellae  of   the  posterior  aponeurosis  of   the  trans- 

versalis. 

It  arises  from  the  last  rib  and  descends,  being-  attached  by 
its  inner  edg-e  to  the  transverse  processes  of  the  lumbar  verte- 
brae, to  be  inserted  into  the  ilium  and  the  Ilio-lumbar  lig-ament. 

Action — It  draws  the  vertebral  column  to  one  side,  and  acts 
as  an  expiratory  ag-ent  by  drawing-  down  the  last  rib.  It  also 
acts  as  an  inspiratory  ag-ent  by  fixing- the  last  riband  prevent- 
ing- the  diaphrag-m  from  drawing-  it  inward.  The  two  muscles, 
acting-  tog-ether  assist  in  flexing-  the  body;  while  either  may 
bend  the  trunk  to  its  own  side. 


222  DESCRIPTIVE  ANATOMY. 

The  nerves  and  arteries  are  from  the  anterior  branches  of 
the  lumbar  nerves  and  arteries. 

Muscles  of  the  Heck. 

When  the  skin  has  been  removed  from  the  neck,  it  reveals 
a  superficial  fascia,  thin  and  delicate,  continuous  below  with 
that  which  covers  the  thorax  and  above  with  that  on  the  face. 
Beneath  this  is  the  Platysma  Myoides  muscle,  and,  on  remov- 
ing- this,  we  encounter  the  dee^  or   investing'  cervical  fascia. 

This  fascia  is  a  dense  membrane  firmly  attached  behind  to  the 
spinous  processes  of  the  cervical  vertebrse,  where  it  blends  with 
the  orig-in  of  the  muscles  in  that  region,  and  completely  encircles 
the  neck.  Below  it  in  part  is  attached  to  the  clavicle  and  sternum 
in  part  it  blends  with  the  deep  fascia  covering-  the  thoracic 
muscles  while  another  portion  passes  into  the  thoracic  cavity 
where  it  blends  with  the  pericardium  and  the  fascia  support- 
ing- the  g-reat  vessels.  Above  it  is  attached  to  the  lower  jaw, 
covers  in  the  parotid  gland  and  g-ives  off  some  bands  consid- 
ered as  ligaments.  Like  all  investing-,  or  enveloping-,  fascias, 
it  divides  into  layers,  or  septa,  which  form  sheaths  for  neig-h- 
boring  muscles,  vessels,  nerves  and  other  structures. 

Leaving  the  cervical  spines  in  a  sing-le  layer,  it  splits  to  en- 
close the  trapezius  ;  uniting,  at  the  anterior  border  of  that 
muscle  to  cover  in  the  triang-ular  interval  between  it  and  the 
Sterno-matsoid,  the  two  layers  ag-ain  divide  and  form  a  sheath 
for  the  litter  muscle,  and,  ag-ain  uniting-,  they  pass  forward 
as  a  single  layer  to  the  midline  of  the  body  in  front,  where 
the  fascia  of  the  opposite  side  of  the  neck  blends  with  the  one 
described.  Of  the  numerous  septa  g-iven  off  from  the  deep 
surface  of  this  fascia  are  :  one  which  forms  a  delicate  sheath 
for  the  infra-hyoid  group  of  muscles  ;  one  which  envelops  the 
trachea,  called  ^re-tracheal  fascia,  and  one  which  passes  in 
front  of  the  pre-vertebral  muscles  and  is  called  the  fre-verte- 
hral  fascia.  From  the  pre-tracheal  and  pre-vertebral  facias  is 
derived  an  important  layer  which  forms  the  sheath  of  the 
carotid  vessels. 

The  muscles  of  the  neck  are  divided  into  a  superficial  and  a 
deep  group;  the  former  containing- two  muscles  and  the  latter, 


THE  MUSCULAR  SYSTEM.  223 

subdivided  into    supra  and  infra-hyoid  groups,   or  elevators 
and  depressors  of  the  h3'0id  bone,  nine. 

Superficial  Group. 

Plat^'sma  Myoides  Sterno-Cleido-Mastoid 

Platysma  Myoides. 

When  the  integ"ument  and  superficial  fascia  have  been  removed 
from  the  front  and  side  of  the  neck  there  is  seen  a  thin  pale 
broad  muscle  called  the  platysma  myoides.  It  arises  from  the 
fascia  coverino-  the  pectoralis  major  and  deltoid  muscles,  and 
passes  upward  and  inward  over  the  clavicle  to  cover  the  side 
and  front  of  the  neck.  Its  innermost  fibres  are  interlocked 
with  the  fi.bres  of  the  opposite  muscle  along-  the  upper  part 
of  the  middle  line  of  the  neck  ;  the  others  are  inserted  into  the 
inferior  maxilla,  some  passing-  over  it  to  be  lost  on  the  side  of 
the  face  and  some  continuing-  to  the  ang-le  of  the  mouth  ;  these 
last  are  joined  by  some  accessory  fibres  which  take  their  orig-in 
on  the  side  of  the  face  from  the  fascia  covering-  the  masseter 
muscle.  These  fibres  have  been  considered  as  a  separate 
muscle  called  risorius  Santorini  or  laug-hing-  muscle. 

Action — It  is  a  depressor  of  the  lower  jaw.  It  can  draw 
the  angle  of  the  mouth  downward  so  as  to  produce  a  melancholy 
expression  or  carry  it  backward  as  in  laug-hing. 

Sterno-Cleido-Mastoid. 

The  sterno-cleido-mastoid  is  the  second  muscle  in  the  su- 
perficial g-roup  and  lies  beneath  the  platysma  between  two 
layers  of  the  deep  cervical  fascia.  It  is  one  of  the  most  im- 
portant muscles  in  the  body  and  derives  its  name  from  its  origin 
and  part  of  its  insertion. 

It  arises  by  a  forked  origin.  One  fork,  a  more  or  less 
rounded  tendon,  springs  from  the  upper  front  part  of  the 
manubrium;  the  other,  musculo-tendinous,  arises  from  about 
the  inner  one-third  or  one-half  of  the  clavicle.  This  origin 
is  very  varible.  An  interval,  filled  by  fibrous  tissue  usually 
exists  between  the  two  heads.  The  muscle  passes  obliquely 
upward,  backward  and  a  little  outward  on  the  side  of  the  neck 
and  is  inserted  into  the   mastoid  portion  of  the  temporal  bone 


224  DESCRIPTIVE  ANATOMY. 

and  adjacent  part  of  the  superior  curved  line  of  the  occipital.. 
Between  its  two  origins  there  is  a  fissure  which  extends  up- 
ward for  some  distance. 

Action — When  both  muscles  act  they  bow  the  head  forward; 
when  one  acts  it  draws  the  head  to  that  side,  turning-  the  face 
somewhat  to  the  opposite  side. 

Depressors  of  the  Hyoid  Bone. 

Sterno-Hyoid  Sterno-Thyroid 

Thyro-Hyoid  Omo-Hyoid 

These  muscles  are  arrang-ed  in  two  layers,  the  two  sterno- 
hyoids and  omo-hyoids  forming-  the  one  in  front  and  the  sterno- 
thyroids and  the  thyro-hyoids  forming-  the  one  behind.  By  their 
inner  edges  the  sterno-hyoids  and  thyro-hyoids  are  in  contact, 
save  for  a  small  triangular  space  just  above  the  sternum.  The 
anterior  belly  of  the  omo-hyoid  is  also, through  the  greater  part 
of  its  course,  in  contact  with  the  outer  edge  of  the  sterno-hyoid. 
After  the  deep  fascia  has  been  removed  these  muscles  are 
widely  separated  and  show  betw^een  them  much  larger  triangu- 
lar spaces  than  really  exist. 

Sterno-Hyoid, 

The  sterno  hyoid  derives  its  name  from  its  attachments.  It 
is  ribbon-like  in  shape  and  vertical  in  direction.  It  arises  from 
the  posterior  aspect  of  the  manubrium  sterni  and  perhaps  from 
the  inner  extremity  of  the  clavicle  or  sterno-clavicular  ligament, 
and  ascends  the  neck  beside  the  middle  line  to  be  inserted  into 

the  hyoid  bone. 

Sterno-Thyroid. 

Lying  behind  the  sterno-hyoid  and  slightly  broader  than  it, 
is  another  ribbon-like  muscle  called, from  its  attachments, 6-/er;^a 
thyroid.  It  arises  from  the  posterior  surface  of  the  manubrium 
and  possibly  from  the  cartilage  of  the  first  rib,  and,  ascending 
beside  the  middle  line  is  inserted  into  the  oblique  ridge  on  the 
ala  of  the  thyroid  cartilage.  Below  it  is  often  traversed  by  a 
tendinous  intersection  as  is  the  sterno-hyoid. 

Thyro-Hyoid. 

The  thyro-hyoid  is  a  short  ribbon-like  muscle  which  con- 
tinues the  course  of  the  sterno-thyroid  to  the  hyoid  bone,  and 


THE  MUSCULAR  SYSTEM.  225 

derives  its  name  from  its  attachments.  It  arises  from  the 
oblique  ridg-e  on  the  ala  of  the  thyroid  cartilage  and  is  inser- 
ted into  the  hyoid  bone.  Frequently  some  of  the  fibres  of  the 
sterno-thyroid  are  continued  directly  into  this  muscle. 

Omo-Hyoid. 

The  oino-hyoid  derives  its  name  from  its  attachments.  It 
is  a  double-bellied  muscle  passing-  with  a  curve  across  the 
side  of  the  neck. 

It  arises  from  the  upper  border  of  the  scapula,  near  the  supra- 
scapular notch,  and  perhaps  from  the  lig-ament  stretched  across 
the  notch  ;  and  passes  forward,  inward  and  slightly'  upward 
until,  beneath  the  sterno-cleido  mastoid,  it  becomes  tendinous, 
its  posterior  belly  ceasing*.  It  then  ag^ain  becomes  fleshy, 
forming-  the  anterior  belly,  and  passes  nearly  upward  but 
with  a  slig-ht  inclination  inward,  to  its  insertion  in  the  hyoid 
bone  at  the  junction  of  its  body  and  g-reater  cornu.  The  cen- 
tral tendon  is  held  down,  so  as  to  g-ive  the  muscle  its  curve, 
by  a  loop  of  fascia  which  is  said  to  pass  to  the  cartilag-e  of  the 
first  rib. 

Action — The  depressors  of  the  h3^oid  bone,  as  the  name  in- 
dicates, draw  the  hyoid  bone  do\vn.  The  sterno-thyroid  draws 
down  the  larynx  and  the  two  omo-hyoids,  acting  together, 
draw"  the  hyoid  bone  downward  and  backward.  The  omo- 
hyoid of  either  side,  acting-  alone,  mig-ht  draw  the  hyoid  bone 
downward,  backward  and  toward  that  side.  The  thyro-hyoids 
have  the  important  action  of  drawing-  the  thyroid  cartilage, 
and  of  course  the  larynx,  upward  under  the  hyoid  bone,  pro- 
tecting- the  larynx  in  swallowing-. 

Nerve  supply  from  descending-  noni.  Arteries  superior  and 
inferior  thyroid. 

Elevators  of  the  Hyoid  Bone. 

Dig-astric  Stylo-Hyoid 

Mylo-Hyoid  Genio-Hyoid 

Genio-Hyo-Glossus 

Digastric. 

The  digastric,   as  its  name    indicates,    is   a  double-bellied 

muscle.     It  is  round  in  shape,  curved  in   direction   and  found 

Des  Anat — 15 


226  DESCRIPTIVE  ANATOMY. 

at  the  upper  part  of  the  side  of  the  neck.  It  arises  fleshy  from 
the  digastric  fossa  of  the  temporal  bone  and  passing-  down- 
ward and  forward,  becomes  tendinous  ;  the  portion  between 
its  origin  and  central  tendon  being  called  the  posterior  belly. 
It  then  again  becomes  fleshy,  forming  the  anterior  belly,  and 
passing  forward  and  upward  is  inserted  into  the  digastric 
fossa  of  the  inferior  maxilla.  The  central  tendon  pierces 
obliquely  the  belly  of  a  small  muscle  which  lies  beside  it 
called  the  stylo-hyoid,  and,  after  emerging  from  it,  plays 
through  a  loop  of  fascia  which  binds  it  down  to  the  hyoid-bone. 

Stylo-Hyoid. 

The  siylo-hyoid  is  a  small  muscle  found  lying  beside  the 
posterior  belly  of  the  digastric  and  deriving  its  name  from  its 
attachments.  It  arises  from  the  outer  side  of  the  styloid 
process  of  the  temporal  bone,  and  passing  downward  and 
forward  is  inserted  into  the  hyoid  bone.  Just  before  its  inser- 
tion it  is  pierced  by  the  central  tendon  of  the  digastric. 

Mylo-Hyoid. 

The  mylo-hyoid  is  a  broad,  thin,  triangular  muscle  which 
forms  the  floor  of  the  mouth.  It  arises  from  the  whole  length 
of  the  mylo-hyoid  ridge,  and,  passing  nearly  inward,  with  a 
slight  inclination  downward,  the  greater  portion  of  the  mus- 
cle meets  its  fellow  of  the  opposite  side  on  the  middle  line, 
forming  a  raphe,  while  some  of  its  posterior  fibres  are  inserted 
into  the  hyoid  bone. 

Genio-Hyoid. 

The  genio-hyoid  is  a  small  muscle  which  slightly  increases 
in  size  as  it  descends.  It  lies  beneath  the  mylo-hyoid  just  be- 
side the  middle  line.  Itarises  from  the  inferior  spina  mentalis 
and  passes  backward  and  slightly  downward  to  be  inserted 
into  the  hyoid  bone. 

Genio-Hy  0-  Glossus. 

^\i^  §eni-hyo-gloss2is  is  a  thin,  radiating  fan-shaped  mus- 
cle. It  arises  by  a  narrow  tendinous  origin  from  the'superior 
spina  mentalis  and  immediately  radiates,  fleshy,  to  be  inserted 
into  the  under  surface  of  the  tongue  from  its  base  to  near  its 


THE  MUSCULAR  SYSTEM.  227 

apex,  some  of  its  lower  fibres  being-  inserted  into  the  hyoid 
bone.  This  muscle  lies  close  to  the  middle  line  beside  its 
fellow. 

Action — The  g-eneral  function  is  that  of  elevation  of  the 
hyoid  bone  or  depression  of  the  lower  jaw.  The  posterior 
bellies  of  the  dig-astrics  can  carry  the  hyoid  upward  and  back- 
ward, while  the  anterior  bellies  carry  it  upward  and  forward. 
The  stylo-hyoid  acts  in  concert  with  the  posterior  belly  of  the 
digastric.  The  posterior  belly  of  one  dig-astric,  and  the  stylo- 
hj^oid  draw  the  hyoid  upward,  backward  and  to  the  side  of  the 
muscle  acting-.  The  mylo-hyoid  acts  like  a  swing*  which  by 
shortening  its  fibres  can  elevate  the  floor  of  the  mouth.  The 
posterior  fibres  can  draw  upward  and  forward  the  hyoid 
bone.  The  genio-hyoid  pulls  the  hyoid  bone,  and  with  it  the 
tongue,  upward  and  forward.  The  g-enio-hyo-g-lossus  may 
pull  the  hyoid  upward,  slightly,  but  its  main  function  is  in 
moving-  the  tongue,  which  it  draws  forward  and  upward. 

Xerves.  Stylo-hyoid  and  posterior  belly  dig-astric  by  the 
facial, — g-enio-hyoid  and  g-enio-hyo-g-lossus  by  ih.Q  hypoglossal ; 
mylo-hyoid  and  anterior  belly  of  dig-astric  by  inferior  dental. 

Surgical  Triangles  of  the  Neck. 

The  side  of  the  neck  presents  a  quadrilateral  surface  which  is 
bounded  below  by  the  clavicle,  above  by  the  body  of  the  inferior 
maxilla  and  an  imaginary  horizontal  line  passing-  from  its 
angle  to  the  mastoid  process  of  the  temporal  bone,  in  front  by 
the  middle  line  and  behind  by  the  anterior  edge  of  the  trape- 
zius. 

This  space. is  subdivided  bv  the  sterno-mastoid  into  k  great 
a?ilc?-io}-  a.nd  3.  g real  foslerior  triang-le.  The  anterior  trian- 
gle is  bounded  as  follows  :  in  front  by  the  middle  line,  behind 
by  the  sterno-cleido-mastoid,  above  by  the  body  of  the  lower 
jaw  and  the  imaginary  line.  The  base  is  above,  the  apex 
below.  Thit  posterior  tria)igle  has  its  base  below,  formed  by 
the  clavicle.  It  is  bounded  in  front  by  the  sterno-cleido-mas- 
toid and  behind  by  the  anterior  edge  of  the  trapezius. 

ICach  of  these  triangles  is  again  subdivided  into  smaller  ones. 
The  anterior  is  divided  into  three  : 


228  DESCRIPTIVE   ANATOMY. 

1st.  The  inferior  carotid  triang-le,  or  triangle  of  necessity^ 
is  bounded  in  front,  by  the  median  line  ;  behind,  by  the  ante- 
rior marg-in  of  the  sterno-mastoid  ;  above,  by  the  anterior 
belly  of  the  omo-hyoid.     Its  base  is  internal. 

2nd.  The  superior  carotid  triang-le,  or  tHang-le  of  election,  is 
bounded  behind  by  the  sterno-mastoid  ;  below,  by  the  anterior 
belly  of  the  omo-hyoid  ;  above,  by  the  posterior  belly  of  the 
digastric.     Its  base  is  external. 

3rd.  The  dig-as  trie  or  suhmaxillary  triang-le  has  its  base 
formed  by  the  lower  jaw  and  the  imaginary  line  and  its  sides 
formed,  posteriorly,  by  the  posterior  belly  of  the  digastric  and 
stylo-hyoid,  anteriorly,  by  the  anterior  belly  of  the  ligastric. 

The  g-reat  -posterior  triangle  is  subdivided  into  two  : 

1st.  The  suboccipital  triang-le  has  its  base  below.  It  is 
bounded  in  front  by  the  sterno-mastoid  ;  behind,  by  the  ante- 
rior edge  of  the  trapezius  ;  below,  by  the  posterior  belly  of 
the  omo-hyoid. 

2nd.  The  subclavian  triangle  has  its  base  below.  It  Is 
bounded  above  by  the  posterior  belly  of  the  omo-hyoid  ;  iu 
front,  by  the  sterno-mastoid  ;  below,  by  the  clavicle.  It  con- 
tains the  subclavian  artery  and  vein,  hence  its  name,  and  the 
brachial  plexus  of  nerves.  In  the  posterior  triangle  the  sub- 
divisions are  made  by  the  posterior  belly  of  the  omo-hyoid  ;  in 
great  anterior  triangle  by  the  anterior  belly  of  the  omo-hyoid, 
and  the  two  bellies  of  the  digastric. 

The  Scaleni  Muscles. 

The  two  scaleni  muscles  form  part  of  a  group  called  f>rce~ 
vertebral. 

The  two  scaleni  muscles  are  distinguished  as  scalenus  anti- 
cits  and  posticus.  A  small  portion  of  the  scalenus  posticus  is 
sometimes  individualized  as  the  scalenus  medius.  These 
muscles  are  of  great  importance  owing  to  the  fact  that  they 
occupy  a  position  in  the  lower  part  of  the  side  of  the  neck,  and 
come  into  important  relation  with  the  subclavian  arterj^  and 
brachial  plexus  of  nerves. 

Scalenus  Anticus. 

The  scalenus  anticus,  triangular  in  shape,  arises  from  the 
anterior  tubercles  of  the  transverse  processes  of   the   third, 


THE  MUSCULAR  SYSTEM.  229 

fourth,  fifth  and  sixth  cervical  vertebrae  by  tendinous  slips, 
which,  uniting-  as  they  descend,  form  the  muscle.  It  is  in- 
serted b}'  a  narrow  tendon  into  the  upper  surface  of  the  first 

rib. 

Scalenus  Posticus. 

The  scalenus  posticus  arises  from  the  posterior  tubercles  of 
the  transverse  process  of  all  the  cervical  vertebrae  except  the 
first.  It  descends  and  divides  into  two  portions,  one  of  which 
is  inserted  into  the  first  rib  between  its  tubercle  and  ang-le — 
and  is  the  part  sometimes  called  scalenus  medius — while  the 
other  goes  to  the  same  point  on  the  second  rib. 

The  scaleni,  acting-  from  above,  draw  up  the  first  and  second 
ribs,  being-  muscles  of  inspiration.  Acting-  from  below  they  can 
draw  the  neck  downward  and  to  the  side  of  the  muscles  acting-; 
or,  the  muscles  of  both  sides  acting-,  can  flex  the  spinal  column. 

The  nerve  supply  is  from  the  lower  three  cervical  nerves. 

Prevertebral  Group. 

Rectus  Capitis  Anticus  Major       Long-us  Colli 

Rectus  Capitis  Anticus  Minor      Rectus  Capitis  Lateralis 

Rectus  Capitis  Anticus  Major. 

This  muscle  arises  from  the  anterior  tubercles  of  the  trans- 
verse processes  of  the  third,  fourth,  fifth  and  sixth  cervical 
vertebra  by  small  tendinous  fasciculi  which  terminate  in  a 
flattened  muscle.  The  muscular  fibres  terminate  in  a  flat 
aponeurosis  which  is  inserted  into  the  basilar  process  of  the 
occipital,  in  front  of  the  foramen  mag-num. 

Rectus  Capitis  Anticus  Minor. 

This  is  a  small  muscle  lying-  beneath  the  preceding-  and  fur- 
ther from  the  mid-line.  It  arises  from  the  transverse  process 
of  the  atlas  and  is  inserted  into  the  basilar  process  of  the  occip- 
ital, slig-htly  external  to  the  preceding-. 

Rectus  Capitis  Lateralis. 

This  muscle  belong-s  properly  to  the  lateral  vertebral  reg-ion 
and  is  an  inter-transverse  muscle.  It  arises  from  the  trans- 
verse process  of  the  atlas  and  is  inserted  into  the  jug-ular  pro- 
cess of  the  occipital. 


230  DESCRIPTIVE  ANATOMY. 

Longus  Colli. 

This  muscle  might  be  appropriately  described  as  three.  One 
arises  from  the  transverse  processes  of  the  third,  fourth  and 
fifth  cervical  vertebrae  and  is  inserted  into  the  transverse  pro- 
cess of  the  atlas.  The  second  arises  from  the  bodies  of  the 
upper  three  dorsal  vertebrae  and  is  inserted  into  the  transverse 
processes  of  the  third  and  fourth  cervical.  The  third  division 
arises  from  the  three  upper  dorsal  and  four  lower  cervical  and 
IS  inserted  into  the  second  and  third  cervical. 

The  muscles  act  so  as  to  flex  and  rotate  the  head  and  cervi- 
cal vertebrae. 

Anterior  branches  from  the  cervical  nerves   supply  these 

muscles. 

The  Muscles  of  the  Back. 

These  muscles  are  arranged  in  several  superimposed  layers 
and  are  covered  by  a  superficial  fascia  which  varies  in  thick- 
ness indifferent  regions.  In  some  situations,  as  in  the  lumbar 
region,  it  usually  contains  a  large  amount  of  fat;  in  other  por- 
tions it  is  a  thick,  loosely  woven  connective  tissue,  not  easily 
divisible  into  layers,  but  everywhere  allows  free  movement 
of  the  skin.  Many  of  the  muscles  arise  from,  or  are  covered 
by,  a  dense  connective  tissue  iovmin^ih.Q.  vertebral  aponeurosis. 
This  fascia  is  attached  to  the  spines  and  transverse  processes 
of  the  vertebrai  from  which  points  it  sends  out  septa  which 
not  only  give  origin  to  muscular  fibres,  but  serve  as  sheaths 
for  some  of  the  muscles. 

First  Layer. 

Trapezius  Latissimus  Dorsi 

Trapezius. 

The  tra-pezius  arises  from  the  superior  curved  line  of  the  oc- 
cipital bone,  from  the  posterior  occipital  protuberance  and  from 
the  spinous  processes  of  all  the  dorsal  and  cervical  vertebrae. 
The  fibres  converge  outward,  some  ascending  obliquel}^,  some 
descending  obliquely  and  some  running  horizontally,  to  reach 
the  insertion  into  the  outer  third  of  the  clavicle,  the  acromion 
process  and  whole  length  of  the  spine  of  the  scapula.  Its 
insertion  is  the  same  as  the  origin  of  the  deltoid. 


THE  MUSCULAR  SYSTEM.  231 

Extending'  from  the  posterior  occipital  protuberance  to  the 
seventh  cervical  /ertebra,  and  attached  to  the  intervening- 
spinous  processes,  is  a  fibrous  cord  called  lig-amentum  nuchas  ; 
and  it  is  in  reality  from  this  cord  that  the  trapezius  arises. 

Nearly  the  whole  of  the  orig-in  of  this  muscle  is  tendinous. 
The  central  portion  of  the  tendon  is  broad  and  thin  and  forms 
a  diamond  shaped  space  between  the  two  muscles. 

Action — According"  to  the  direction  of  the  fibres  which  act  it 
can  draw  the  scapula  directly  backward,  downward  and  back- 
ward or  upward  and  backward. 

Latissimus  Dorsi. 

The  latisshmis  dorsi  arises  from  the  spinous  processes  of 
the  lower  four  or  six  dorsal  vertebrs,  all  the  lumbar  vertebrae 
and  fhe  spinous  tubercles  of  the  sacrum,  from  the  p^osterior 
third  of  the  crest  of  the  ilium  and  by  fleshy  slips  from  the 
three  or  four  lower  ribs.  The  muscle  is  tendinous  at  its  ori- 
gin except  that  part  arising*  from  the  ribs.  As  it  passes  up- 
ward and  outward  the  fibres  converg-e,  become  thicker  and 
fleshy  and  passing-  over  the  lower  ang-le  of  the  scapula,  wind 
around  the  teres  major  to  be  inserted  along-  with  it  into  the 
posterior  bicipital  ridg-e  of  the  humerus.  The  tendon  of  the 
teres  major  is  wider  and  extends  further  down  on  the  humerus 
than  that  of  the  latissimus  dorsi. 

Action — It  carries  the  humerus  downward  and  backward, 
rotates  it  inward,  is  an  inspiratory  ag-ent,  and,  when  the 
humerus  is  fixed,  as  in  climbing-  or  using-  crutches,  it  moves 
the  body  forward. 

The  trapezius  is  supplied  by  the  spinal  accessory  and 
branches  from  the  anterior  divisions  of  the  third  and  fourth 
cervical.  The  long-  sub-scapular  supplies  the  latissimus 
dorsi. 

Second  Layer. 

Levator  Ang-uli  Scapula;  Rhomboideus 

Levator  Anguli  Scapulae. 

The  levator  aiif^uli  scapuhc  arises  by  tendinous  slips  from 
the  posterior  tubercles  of  the  transverse  processes  of  the  four 


232  DESCRIPTIVE  ANATOMY. 

Upper  cervical  vertebrae.  These  slips  unite  to  form  the  belly 
of  the  muscle  which  descends  obliquely  outward  to  be  inserted 
into  the  posterior  border  of  the  scapula  from  the  angle  to 
the  intersection  of  the  spine  with  that  border. 

This  muscle  draws  the  shoulder  upward  and  inward,  or, 
actino-  from  below,  inclines  the  neck  and  head  to  that  side, 
rotating"  them  at  the  same  time. 

The  nerve  for  the  levator  is  from  the  anterior  divisions  of 
the  third  and  fourth  cervical. 

Rhomboideus. 

The  rhoniboideiis  arises  from  the  spinous  processes  of  the 
last  cervical  and  four  upper  dorsal  vertebrae,  and  passing-  down- 
ward and  outward  is  inserted  into  the  posterior  border  of  the 
scapula  as  far  as  the  inferior  ang-le.  Some  make  two  muscles 
of  this,  calling"  the  portion  which  arises  from  the  cervical  ver- 
tebra rhomboideus  minor  and  that  arising"  from  the  dorsal  ver- 
tebrae rhomboideus  major. 

Action — It  moves  the  scapula  upward  and  backward,  so  as 
to  bring"  the  two  scapulae  nearer  tog"ether. 

Third  Layer 

Serratus  Posticus  Superior         Serratus  Posticus  Inferior 

Splenius 

Serratus  Posticus  Superior. 

The  serratus  -posticus  superior  has  a  tendinous  origin  from 
the  spinous  processes  of  the  two  lower  cervical  and  two  upper 
dorsal  vertebrae.  It  passes  downward  and  outward  and  is  in- 
serted by  fleshy  serrations  into  the  upper  borders  of  the  second, 
third,  fourth  and  fifth  ribs  just  beyond  their  ang"les. 

Action — It  is  an  inspiratory  agent. 

Serratus  Posticus  Inferior. 

The  serratus  posticus  inferior  has  a  tendinous  orig"in  from 
the  spinous  processes  of  the  last  two  dorsal  and  first  two  lum- 
bar vertebrae.  It  passes  upward  and  outward  and  is  inserted 
by  fleshy  slips  into  the  lower  borders  of  the  last  four  ribs. 

Action — It  is  an  expiratory  agfent. 


THE  MUSCULAR  SYSTEM.  233 

Splenius. 

The  sploiins  arises  from  the  spinous  processes  of  the  four 
lower  cervical  vertebrae  and  four  or  six  upper  dorsal  vertebras. 
It  ascends  and  divides  into  two  portions,  one,  known  as  the 
spioiiKs  capitis,  is  inserted  into  the  occipital  bone  between  its 
curved  lines  and  into  the  mastoid  portion  and  process  of  the 
temporal  bone  ;  the  other,  called  splenius  colli,  is  inserted 
into  the  posterior  tubercles  of  the  transverse  processes  of  the 
three  upper  cervical  vertebras. 

Action — It  bends  the  head  and  upper  part  of  the  spine  back 
and  rotates  the  head  toward  its  side. 

Erector  Spinae. 

This  powerful  muscle  occupies  a  larg^e  portion  of  the  vertebral 
^•roove,  extending-  from  the  sacrum  upward  until  its  prolong-a- 
tions  may  be  traced  throug-h  the  cervical  reg^ion.  It  is  held 
down  in  position,  throug-h  a  larg-e  portion  of  its  course,  by 
the  powerful  vertebral  aponeurosis,  call  by  different  names  in 
the  different  reg-ions.  In  the  lumbar  region,  where  it  is  most 
powerful,  it  is  continuous  with  the  aponeurosis  forming-  the 
sheath  of  the  quadratus  lumborum. 

The  erector  spincc  arises  by  tendinous  fibres  from  the  back 
of  the  sacrum,  occup^ang-  the  whole  of  the  sacral  groove  ; 
from  the  posterior  part  of  the  crest  of  the  ileum  :  from  the 
great  sacro-sciatic  ligament  and  from  the  spinous  processes 
of  the  lumbar  vertebrae.  This  larg-e  mass  passes  upward  and, 
about  opposite  the  last  rib,  it  divides  into  two  portions,  the 
ilio-costalis,  which  is  inserted  into  the  seven  lower  ribs  and 
the  lonn-issiiims  dorsi  which  is  inserted  into  the  transverse 
processes  of  the  dorsal  vertebras  and  into  nearly  all  the  ribs, 
this  portion  of  the  insertion  being-  very  variable.  Between 
these  two  divisions  lies  an  accessory  muscle,  called  musculns 
ucccssorius  which,  arising-  from  the  ang-les  of  the  six  lower, 
is  inserted  into  the  ang-les  of  its  six  upper  ribs.  Continuing- 
this  upward  is  the  cervicalis  ascendcus  which,  spring-ing-  from 
the  ang-les  of  the  four  upper  ribs  is  inserted  into  the  posterior 
tubercles  of  the  transverse  processes  of  the  fourth,  fifth  and 


234  DESCRIPTIVE  ANATOMY. 

sixth  cervical  vertebrae.  In  like  manner  the  long-issimus  dorsi 
is  continued  upward  by  an  inner  set  of  fibres  the  traiisversalis 
colli  which  spring's  from  the  transverse  processes  of  the  six 
upper  dorsal  and  is  inserted  into  the  cervical  as  hig-h  as  the 
second  ;  and  the  trachelo-mastoid  which  arises  from  the  trans- 
verse processes  of  the  dorsal  vertebrae  from  the  second  to  the 
sixth  is  inserted  into  the  mastoid  process. 

Beside  these  there  are  two  small  muscular  masses,  the  spi-- 
nalis  dorsi,  in  the  lumbar,  and  spinalis  colli  in  the  cervicaj 
regfion  which  spring*  from  the  transverse  processes  below  and 
are  inserted  into  those  above.  They  are  really  part  of  the 
attachment  of  the  long-issiumses  dorsi.  The  complexus  is  a 
somewhat  similar  offshoot  of  the  trachelo-mastoid  arising-  by 
slips  from  the  upper  seven  dorsal  and  last  cervical  vertebrae 
to  be  inserted  into  the  occipital  between  the  curved  lines. 

The  name  almost  sufficiently  g"ives  the  action  of  the  erector 
spin« — it  keeping-  the  body  in  the  erect  posture.  It  can  also 
bend  the  spine  backward,  or  backward  and  to  one  side  when 
one  muscle  alone  acts. 

This  muscle  is  supplied  by  the  posterior  divisions  of  the 
spinal  nerves  in  the  cervical  dorsal  and  lumbar  reg-ions. 

Beneath  this  layer  there  is  another  of  small  muscles  which 
barely  deserve  mention.  The  most  important  being-  the  rectus 
capitis  posticus  major  and  minor,  the  former  spring-ing-  from 
the  spinous  process  of  the  axis  and  being-  inserted  into  the 
inferior  curved  line  of  the  occipital;  the  latter  arising-  from  the 
tubercle  of  the  atlas  and  being-  inserted  into  the  occipital 
internal  to  the  preceding-  muscle. 

The  Muscles  of  the  Thorax. 

Triangularis  Sterni. 

The  triangularis  sterni  is  found  on  the  posterior  aspect  of 
the  front  wall  of  the  chest  on  either  side  of  the  sternum.  It 
arises  from  the  edg-e  of  the  sternum  and  from  the  costal  carti- 
lag-es  from  the  third  to  the  sixth  or  seventh,  and,  passing* 
upiL'a7'd  3Lnd  outzuard,  is  inserted  into  the  second,  third,  fourth 


THE  MUSCULAR  SYSTEM.  235 

and  fifth  costal  cartilag'es  and  corresponding'  ribs.  Its  inser- 
tion corresponds  to  that  of  its  antag-onist  the  serratus  posticus 
superior. 

Action — It  is  an  expiratory  ag"ent. 

Intercostal  Muscles. 

The  interval  between  two  ribs  is  occupied  by  two  layers  of 
muscular  fibres  which  extend  between  the  edges  of  adjacent 
ribs  and  are  known  as  external  and  internal  intercostal  muscles. 

Anterior  Thoracic  Region. 

Pectoralis  Major         Pectoralis  Minor         Subclavius 

The  muscles  of  this  region  are  covered  by  the  usual  super- 
ficial fascia  and  by  a  deep  fascia  which  partly  blends  with  that 
of  the  cervical  and,  at  the  side,  with  that  covering  the  axil- 
lary space. 

Pectoralis  Major. 

The  pectoralis  Diajor  derives  its  name  from  its  position  on 
the  front  of  the  chest,  and  from  the  fact  that  there  is  another 
muscle  smaller  than  it  in  the  same  region.  It  is  coarse  in 
structure,  triangular  in  shape  with  its  base  within  and  apex 
without.  It  arises  fleshy  from  the  sternal  two-thirds  of  the 
clavicle,  from  the  whole  length  of  the  front  of  the  sternum 
and  from  the  cartilages  of  five  ribs,  /.  e.  all  of  true  ribs  except 
the  first  and  seventh  (this  origin  being*  by  fibres  which  rein- 
force the  muscle  as  it  passes  over  the  ribs)  and  from  the 
aponeurosis  of  the  external  oblique  muscle  of  the  abdomen. 

The  fibres  converge  as  the}-  pass  outward.  Those  from  the 
clavicle  pass  nearly  vertically  downward,  those  from  the  lower 
part  of  the  sternum  and  the  aponeurosis  of  the  external 
oblique  pass  obliquely  upward  and  outward  and  the  intermedi- 
ate fibres  pass  hori/.ontally  outward.  They  all  terminate  in  a 
folded  tendon  which  is  inserted  into  the  anterior  bicipital 
ridge  of  the  humerus.  As  the  fibres  are  approaching  their 
termination  some  fold  over  the  others,  those  from  the  lower 
portion  of  the  origin  of  the  muscle  passing  behind  and  forming 
the  upper  part  of  the  tendon,  those  from  the  clavicle  passing 
in  front  and  forming  the  lower  part  of  the  tendon. 


236  DESCRIPTIVE  ANATOMY. 

Action — It  draws  the  humerus  across  the  chest  slig'htly 
rotating-  the  arm  inward.  If  the  arm  be  raised  it  will  aid  the 
latissimus  dorsi  in  drawing-  it  downward,  or,  acting-  from  above 
in  drawing-  the  body  up^vard.  Both  it  and  the  next  muscle 
thus  act  as  inspiratory  ag-ents. 

Pectoralis  Minor. 

The  pectoralis  minor  derives  its  name  from  its  position  on 
the  front  of  the  chest,  and  from  the  fact  that  there  is  another 
pectoral  muscle  of  larg-er  size.  It  is  found  beneath  the 
pectoralis  major,  is  small  in  size,  oblique  in  direction  and  tri- 
ang-ular  in  shape.  It  arises  from  the  front  of  the  third,  fourth 
and  fifth  ribs,  passes  upward  and  outward,  fleshy,  narrows  to 
a  tendon  and  is  inserted  into  the  coracoid  process  of  the 
scapula. 

Action — Rotates  the  scapula  on  the  thorax  and,  when  the 
scapula  is  fixed,  aids  in  expanding-  the  chest. 

Subclavius. 

The  subclavius  derives  its  name  from  its  position  just  be- 
neath the  clavicle.  It  is  a  small  round  muscle  which  arises 
from  the  cartilag-e,  and  possibly  the  adjacent  osseous  portion, 
of  the  first  rib  by  a  tendon,  it  passes  horizontally  outward, 
becomes  fleshy,  and  almost  immediately  after  it  ceases  to  rise, 
beg-ins  to  be  inserted,  its  belly  being-  extremely  short,  into 
the  whole  length  of  the  g-roove  on  the  under  surface  of  the 
clavicle.  This  g-roove  occupies  about  the  middle  one-third  of 
the  clavicle. 

Action — It  draws  the  clavicle  downward. 

Thoracic  Surgical  Triangle. 

Lying-  just  above  the  subclavius,  which  is  sometimes  g*iven 
as  its  upper  limit,  is  a  triang-ular  space  of  surgical  importance. 
It  is  bounded  above  by  the  clavicle,  below  by  the  upper  edge 
of  the  pectoralis  minor;  its  apex  is  without  and  is  crossed  by 
the  auxiliary  vessels  and  nerves;  its  base  is  within  and  is 
formed  by  an  imaginary  line  drawn  from  the  inner  extremity 
of  the  clavicle  to  the  commencement  of  the  origin  of  the  pecto- 
ralis minor. 


THE  MUSCULAR  SYSTEM.  237 

Lateral  Thoracic  Region. 
Serratus  Magnus. 

The  serratus  mag-}ms  is  a  larg-e  thin  muscle  found  upon  the 
side  of  the  chest  wall.  It  derives  its  name  from  its  extensive 
origin  by  means  of  diofitations  or  serrations. 

It  arises  by  nine  digfitations  from  the  outer  surface  of  the 
eight  upper  ribs,  the  lower  five  interlocking  with  serrations 
of  the  external  oblique,  and  two  arising  from  the  second  rib. 
Its  origin  is  fleshy,  and  it  continues  its  course,  fleshy,  outward 
and  backward  over  the  side  of  the  chest,  to  be  inserted  into 
the  whole  length  of  the  anterior  edge  of  the  posterior  border 
of  the  scapula. 

Action — It  moves  the  scapula  on  the  thorax  and,  when  the 
scapula  is  fixed,  raises  the  ribs. 

Acromial  Region. 
Deltoid. 

A  single  muscle  constitutes  this  region,  the  deltoid,  so  named 
from  its  supposed  resemblance  to  an  inverted  Delta.  It  is  a 
large,  coarse  muscle,  triangular  in  outline,  forming  the  bulge 
of  the  shoulder,  and  corresponding  in  a  measure  to  the  Glu- 
teus Maximus  of  the  lower  extremity.  Its  base  is  directed 
upward  and  its  apex  downward.  Its  origin  is  extensive,  con- 
sisting of  musculo-tendinous  fibres,  which  arise  from  the  outer 
one-third  of  the  anterior  border  of  the  clavicle,  from  the  ac- 
romion process,  and  whole  length  of  the  posterior  border  of  the 
spine  of  the  scapula,  and  by  some  fibres  from  the  intervening 
fascia  covering  the  infraspinatus  muscle.  The  fibres  converge 
as  they  descend,  the  posterior  passing  forward  and  downward, 
the  anterior  downward  and  backward,  and  the  central  vertically 
downward,  until  they  form  a  short,  thick  tendon,  which  is  in- 
serted into  a  V-shaped  impression  about  half-way  down  the 
outer  surface  of  the  shaft  of  the  humerus. 

Action,  Its  posterior  fibres  carry  the  humerus  upward  and 
backward  its  anterior  fibres  upward  and  forward.  By  its 
central  fibres,  which  act  in  concert  with   the  supraspinatus, 


238  DESCRIPTIVE  AN  ATONY. 

the  humerus  is  carried  directly  away  from  the  body  until  it  is 
at  right  ang-les  with  the  body. 

The  posterior  circumflex  nerve  and   the  circumflex  arteries 
supply  this  muscle. 

The  Scapular  Group. 

Subscapularis  Teres  Minor 

Supraspinatus  Infraspinatus  Teres  Major 

The  Scapular  Grouf>  of  Muscles  consists  of  the  subscapularis, 
the  supraspinatus ,  the  infraspinatus ,  the  teres  major  and  the 
teres  minor  (L.  Teres,  long- and  round).  Three  of  these  mus- 
cles, it  will  be  seen,  are  named  from  the  fossae  w^hich  they 
occupy  upon  the  scapula,  the  other  two  being  named  from  their 
supposed  shape,  "round  muscles".  In  the  description  of  the 
scapula  it  was  stated  that  both  on  the  back  and  on  the  front 
the  fossae  described  did  not  occupy  the  entire  aspect  of  the 
bone,  hence  in  studying  the  origin  of  these  muscles  it  is  unnec- 
essary to  point  out  the  exceptions  of  the  anterior  lip  of  the 
posterior  border  for  instance,  but  simply  to  except  that  part 
of  the  fossa  from  which  the  muscle  fails  to  rise,  and  not  that 
part  of  the  anterior  or  posterior  surface  of  the  scapula. 

Subscapularis. 

The  subscapularis,  the  first  of  these  muscles,  is  a  coarse, 
flat  muscle,  which  occupies  the  entire  subscapular  fossa;  but 
does  not  rise  from  the  whole  of  it,  nor  from  the  whole  length 
of  the  scapula.  It  rises  from  the  entire  subscapular  fossa, 
with  the  exception  of  its  external  one-third;  and  also  from  the 
fascia  which  invests  the  entire  muscle,  and  from  septa  sent 
down  from  this  fascia  between  the  bundles  of  muscular  fibre 
to  seize  the  ridges  of  the  subscapular  fossa  and  from  an  aponeu- 
rosis which  separates  the  teres  major  and  form  the  long  head 
of  the  triceps. 

These  fibres  converge,  the  superior  one  passing  nearly  directly 
forward  and  outward,  the  central  ones  having  a  slightly  ob- 
lique direction  upward,  outward  and  forward, while  the  inferior 
fibres  run  nearly  directly  upward,  outward  and  forward.  It 
narrows  to  a  tendon,  thick  and  strong,  which  passes  over  the 


THE  MUSCULAR  SYSTEM.  239 

neck  of  the  scapula,  crosses  the  head  of  the  humerus,  and  is 
inserted  into  the  lesser  tuberosity  of  the  humerus  and  into  the 
bone  for  about  an  inch  below,  blending-  with  the  fibres  of  the 
capsular  ligfament  of  the  shoulder  joint. 

Action.  It  is  chiefly  an  inward  rotator  of  the  humerus;  but 
its  inferior  fibres  have  a  slig-ht  effect  in  drawing-  the  humerus 
downward  when  it  has  been  elevated,  and  carrying-  it  back- 
ward after  it  has  reached  the  vertical  position. 

Subscapular  nerves  and  arteries  supply  it. 

Supraspinatus. 

The  siiprasf>iiiatus  rises  from  the  whole  of  the  supraspinous 
fossa,  except  its  outer  one-third,  and  from  the  interveniug- 
fascia,  which  completely  covers  the  muscle.  It  is  a  triang-ular 
muscle,  which  converg-es  as  it  passes  forward  and  outward, 
forms  a  tendon  which  runs  under  the  acromion  process  of  the 
scapula,  and  which  is  inserted  into  the  hig-hest  of  the  three 
muscular  impressions  found  on  the  g-reater  tuberosity  of  the 
humerus,  the  lower  fibres  of  the  tendon  blending-  with  the 
capsular  lig-ament. 

Action.  It  aids  the  deltoid  in  raising-,  or  abducting-,  the 
humerus  until  it  is  at  rig-ht  ang-les  to  the  body  ;  and  is  to  a 
slig-ht  extent  an  outward  rotator. 

Suprascapular  nerve  and  artery  supply  it  and  the  following- 
muscle. 

Infraspinatus. 

The  Infraspinatus  rises  from  the  whole  infraspinous  fossa, 
execpt  its  outer  third,  from  the  investing-  fascia,  which  covers 
the  muscle,  and  from  the  inter-muscular  septa  sent  down  be- 
tween itself  and  the  teres  major  below  and  the  teres  minor 
above  near  the  axillary  border  of  the  scapula.  Like  its 
predecessor,  the  fibres  converg-e  to  form  a  tendon,  which 
passing-  behind  the  shoulder  joint,  blends  with  the  capsular 
lig-ament,  and  is  then  inserted  into  the  middle  of  the  three 
muscular  impressions  on  the  g-reater  tuberosity  of  the  humerus. 

Action.  Its  action  is  almost  entirely  confined  to  external 
rotation  of  the  humerus. 


240  DESCRIPTIVE  ANATOMY. 


Teres  Minor. 

The  teres  minor  rises  from  the  upper  two-thirds  of  the  ax- 
illary border  of  the  scapula,  with  the  exception  of  the  space 
occupied  by  the  long-  head  of  the  Triceps.  It  also  rises  from 
the  inter-muscular  septum  between  itself  and  the  infraspinatus 
internally  and  itself  and  the  teres  major  externally,  and  from  the 
fascia  which  covers  the  lower  portion  of  the  muscle.  Its  di- 
rection is  upward  and  outward.  The  tendon  narrows  but 
sligfhtly  and  after  blending-  wnth  the  fibres  of  the  capsular  lig- 
ament, is  inserted  into  the  lowest  of  the  three  muscular  im- 
pressions on  the  g-reater  tuberosity  of  the  humerus,  and  into 
the  bone  for  a  short  distance  below. 

Action.  Like  its  predecessor,  its  chief  action  is  that  of  ex- 
ternal rotation  of  the  humerus. 

Supplied  by  branch  from  the  circumflex. 

Teres  Major. 

The  teres  major  lies  just  below  the  te^-es  minor,  from 
which,  after  its  orig-in,  it  is  separated  by  a  widening-  interval. 
It  rises  from  the  lower  one-third  of  the  axillary  border  of  the 
scapula,  and  from  that  portion  of  the  dorsum,  called  the  infer- 
ior angle,  which  does  not  enter  into  the  infraspinous  fossa. 
'  It  also  rises  from  the  intervening  fascia,  which  covers  the 
lower  portion  of  the  muscle,  and  from  inter-muscular  septa 
between  itself  and  the  teres  minor  above  and  the  infraspinatus 
below.  From  this  origin  it  passes  upward,  outward  and 
forward,  its  upward  obliquity  being-  less  than  that  of  the  teres 
minor;  and  is  inserted  by  a  broad,  flat  tendon  into  the  internal 
bicipital  ridg-e  of  the  humerus. 

Action.  It  draws  the  humerus  downward  and  backward, 
acting-  here  in  concert  with  the  latissimus  dorsi;  and  is  also  an 
inward  rotator.     Supplied  by  lower  subscapular. 

Between  the  two  teres  muscles  is  a  surgical  triang-le  of 
some  importance,  the  base  of  which  is  directed  towards  the 
humerus,  and  the  apex  towards  the  scapula.  This  triang-le 
is  bounded  above  by  the  lower  border  of  the  teres  minor,  be- 
low by  the  upper  border  of  the  teres  major,  and  externally  by 


THE  MUSCULAR  SYSTEM.  241 

that  portion  of  the  shaft  of  the  humerus  which  intervenes 
between  the  teres  muscles.  This  space  is  subdivided  by  the 
long-  head  of  the  triceps  into  an  external  quadrilateral  and  an 
internal  triang-ular  space.  The  triang-ular  space,  of  small 
importance,  is  bounded  above  by  the  lower  border  of  the  teres 
minor,  below  by  the  upper  border  of  the  teres  major,  and 
anteriorly  by  the  long-  head  of  the  triceps.  The  quadrilat- 
eral space  is  bounded  behind  by  the  long-  head  of  the  triceps, 
in  front  by  the  shaft  of  the  humerus,  above  by  the  lower 
border  of  the  teres  minor,  and  below  by  the  upper  border  of 
the  teres  major.  Through  this  space  pass  important  blood- 
vessels and  nerves. 

The  Muscles  and  Fascia  of  the  Humerus,  or  Arm. 

The  muscles  of  the  humerus,  or  arm,  are  invested  by  fascia, 
constituting-  a  portion  of  the  fascia  of  the  upper  extremity, 
which  completely  envelops  the  limb.  In  front  it  is  continuous 
with  the  fascia  which  envelops  the  pectoral  muscles,  poste- 
riorly with  that  which  invests  the  posterior  scapular  g-roup, 
internally  with  the  fascia  which  forms  the  floor  of  the  axillary 
space,  and  externally  with  the  fascia  investing-  the  deltoid 
muscle.  As  this  fascia  descends  the  arm  it  sends  in  two 
septa,  one  from  either  side.  The  internal  inter-muscular 
septum  is  attached  to  the  internal  border  of  the  humerus,  the 
internal  condyloid  ridg-e,  and  to  the  internal  condyle  of  the 
humerus.  The  external  inter-muscular  septum  is  likewise 
attached  to  the  external  border,  external  condyloid  ridge,  and 
external  condyle  of  the  humerus. 

These  inter-muscular  septa  not  only  serve  to  separate  the 
anterior  from  the  posterior  groups;  but  they  also  g-ive  a  firm 
and  unyielding  orig-in  to  the  various  muscles  of  the  arm  and 
forearm. 

The  Muscles  of  the  Arm  are  divided  into  two  g-roups  :  the 
Anterior  and  Posterior  Humeral  Groups. 

Anterior  Humeral  Group. 

Biceps  Flexor  Coraco-Brachialis 

Brachialis  Anticus 

Des  Anat — 16 


242  DESCRIPTIVE  ANATOMY. 

Biceps. 

The  biceps  (Iv.  bis,  twice  ;  caput,  head),  as  its  name  indi- 
cates, has  a  double  orig-in,  one  called  the  "long-"  and  the  other 
the  "short"  head.  The  short  head  arises  by  musculo-tendi- 
nous  fibres  from  the  coracoid  process  of  the  scapula,  in  common 
with  the  coraco-brachialis.  It  descends  blended  with  this 
muscle  for  its  upper  two  inches,  and  then  no  longer  blended, 
but  parallel,  with  the  coraco-brachialis,  to  the  insertion  of 
that  muscle,  where  it  is  joined  by  the  lo^ig-  head,  which  arises 
from  the  upper  border  of  the  g-lenoid  cavity  of  the  scapula, 
where  it  blends  with  the  g-lenoid  ligament.  By  tendinous 
fibres  the  long  head  passes  over  the  shoulder  joint  in  a  sepa- 
rate synovial  sheath  ;  and  blends  about  the  middle  of  the 
humerus  with  the  short  head  to  form  the  belly  of  the  muscle. 
The  belly  of  the  muscle  so  formed  passes  down  the  front  of 
the  arm  to  near  the  elbow^  where  it  terminates  in  a  tendon, 
which  gives  off  a  strong  slip  of  fascia  to  blend  with  the  invest- 
ing fascia  of  the  forearm,  while  the  bulk  of  the  tendon  is 
inserted  into  the  posterior  part  of  the  bicipital  tuberosity  of 
the  radius. 

Action.  It  is  a  flexor  of  the  forearm  ;  but  its  short  head, 
if  acting  alone,  may  to  a  trifling  extent  abduct  the  forearm, 
and  the  long  head  to  some  extent  can  adduct  it.  With  the 
forearm  in  a  position  of  pronation,  the  muscle  becomes  the 
most  powerful  of  the  supinators  of  the  forearm.  It  is  also  a 
tensor  of  the  deep  fascia  of  the  forearm.  The  biceps  is  sup- 
plied by  the  musculo-cutaneous  nerve. 

Coraco-Brachialis. 

The  Coraco-brachialis,  arises  in  common  with  the  short 
head  of  the  biceps  from  the  coracoid  process  of  the  scapula, 
passes  down  on  the  inner  side  of  that  muscle,  adherent  to  it 
for  about  two  inches,  and  then  in  contact  with  it,  but  no  longer 
adherent  to  it,  to  the  middle  of  the  arm,  where  it  is  inserted 
in  the  middle  of  the  internal  face  of  the  shaft  of  the  hmerus. 

Action.  It  is  a  flexor  of  the  arm  ;  and  can,  acting  in  concert 
with  the  short  head  of  the  biceps,   aid  that   muscle,   though 


THE  MUSCULAR  SYSTEM.  243 

acting"  more  powerfully,   in   carrying-  the  arm   inward,  or  ad- 
ductingf  it.     It  is  supplied  by  the  musculo-cutaneous  nerve. 

Brachialis  Anticus. 

The  Brachialis  Anticus  is  a  bulky  mass  lying-  deeper  than 
the  preceding-  muscles  on  the  lower  part  of  the  front  of  the 
arm.  It  arises  by  two  dig-itations,  so  arrang-ed  as  to  embrace 
the  V-shaped  insertion  of  the  deltoid,  and  expanding-  from 
that  point  down  the  shaft  of  the  humerus  to  within  an  inch 
of  the  elbow  joint,  its  origin  covering-  the  whole  front  of  the 
humerus  between  these  two  points.  It  also  spring-s  from  the 
whole  of  the  internal  inter-muscular  septum,  and  from  the 
upper  portion  of  the  external  inter-muscular  septum,  being- 
cut  off  from  the  latter  by  the  orig-in  of  the  supinator  long-us 
and  extensor  carpi  radialis  long-ior.  It  narrows  to  a  triang-u- 
lar  tendon,  which  passes  over  the  elbow,  and  is  inserted  into 
the  front  of  the  coronoid  process  of  the  ulna. 

Action.  It  is  a  pow^erful  flexor  of  the  forearm  upon  the 
arm,  thoug-h  in  some  positions  of  the  body — ^as  in  "chinning-" 
a  bar — it  flexes  the  arm  upon  the  forearm,  acting-,  as  all  mus- 
cles do,  from  either  extremity.  It  is  supplied  by  the  musculo- 
spiral  and  musculo-cutaneous  nerves. 

Posterior  Humeral  Group. 

Triceps. 

The  tricefts  is  a  larg-e  fleshy  mass.  It  covers  the  w^hole  of 
the  posterior  face  of  the  humerus,  being  the  onh'  muscle  found 
in  that  situation.  It  rises  by  three  heads  :  the  middle,  or 
long;  the  internal,  or  short ;  and  the  external,  or  intermediate. 
The  long-  head  ^x'vryQ.^  from  the  upper  one-inch  of  the  axillary 
border  of  the  scapula  by  tendinous  fibres. 

The  short  head  a.r\%c%  from  the  inner  one-half  of  the  poste- 
rior face  of  the  humerus,  and  the  posterior  face  of  the  inter 
nal  muscular  septum  and  the  intermediate  arises  from  the  ex- 
ternal half  of  the  posterior  face  of  the  humerus,  and  the 
external  inter-muscular  septum.  The  three  heads  blend 
tog-ether  to  form  the  belly  of  the  muscle,  which  passing-  down- 
ward becomes  tendinous,  the  tendinous  fibres  extending-  much 


244  DESCRIPTIVE  AN  ATONY. 

further  up  on  its  posterior  than  on  its  deep,  or  anterior,  aspect, 
to  be  ultimately  inserted  into  the  depressed  surface  on  the 
upper  extremity  of  the  olecranon  process  of  the  ulna.  The 
muscle  can  be  more  briefly  described  by  saying  that  the  inner 
and  the  external  of  the  heads  rise  from  the  whole  of  the  pos- 
terior surface  of  the  shaft  of  the  humerus,  the  former  begin- 
ning* at  the  insertion  of  the  Teres  major  and  the  latter  at  the 
insertion  of  the  Teres  minor.  Between  these  is  found  the, 
long  head,  arising  at  the  upper  inch  of  the  axillary  border  of 
the  scapula.  They  all  blend  to  reach  the  insertion  above 
mentioned. 

Action. — This  muscle  is  the  extensor  of  the  forearm  upon 
the  arm;  but  its  long  head  being  attached  to  the  scapula  and 
passing  over  two  joints,  approximates  the  head  of  the  humerus 
to  the  Glenoid  cavity,  and  slightly  aids  other  muscles  in  draw- 
ing the  humerus  backward.  It  may  also  in  climbing  draw 
the  scapula,  and  if  that  be  fixed,  the  body,  upward  on  the 
humerous. 

It  is  supplied  by  the  musculo  spiral  nerve. 

The  Muscles  of  the  Fore- Arm. 

Before  reaching  the  muscles  of  the  forearm  we  find  that 
portion  of  the  upper  extremity  enveloped  in  a  strong  fibrous 
membrane, called  the  Deep  or  Investing  Fascia  of  the  Forearm. 
This  membrane  is  first  attached  to  the  olecranon  process  of  the 
Ulna  and  passes  downward  attached  to  the  posterior  border  of 
the  shaft  of  the  Ulna.  Passing  forward  on  either  side,  it  is 
attached  to  the  internal  and  external  condyles  of  the  humerus, 
and  then  uniting  over  the  front  of  the  limb  forms  a  complete 
investment.  From  this  investing  sheet  septa  are  sent  off, 
which  not  only  serve  the  purpose  of  dividing  the  different  layers 
from  one  another,  but  which  also  serve  to  give  a  strong  and 
firm  attachment  to  the  muscles  which  belong  to  this  portion 
of  the  upper  extremity.  Some  of  these  muscles  arise  from 
the  fascia  as  a  strictly  investing  membrane,  while  others  arise 
from  the  intermuscular  septa,  which  are  tongues  of  fascia 
sent  down  between  the  different  muscles  or  groups  of  muscles. 
Thus  the  whole  limb  is  divided  into  separate  compartments, 


THE  MUSCULAR  SYSTEM.  245 

SO  that  could  a  muscle  be  dissolved  out  without  affecting*  the 
fascia,  it  would  be  found  to  have  its  separate  and  distinct  com- 
partment, as  would  be  the  case  for  all  of  the  muscles  of  the 
limb.  This  fascia  becomes  particularly  strong"  and  dense  at 
the  wrist  joint,  where  it  sends  across  both  on  the  front  and 
the  back  strong-  braces,  which  are  respectively  known  as  the 
A f/terior  a.nd  Posterior  Annular  Ligaments. 

The  Posterior  is  an  oblique  band,  which  passes  downward 
and  inward  across  the  back  of  the  wrist,  and  is  attached  by 
one  extremity  to  the  lower  end  and  styloid  process  of  the 
radius  and  by  the  other  to  the  cuneiform  and  pisiform  bones. 
It  binds  the  tendons  of  the  Extensor  muscles  down  upon  the 
bones,  and  it  sends  down  septa  which  form  six  separate  com- 
partments throug-h  which  these  tendons  pass. 

The  Anterior  Annular  Ligament  is  less  well  marked  than 
is  the  Posterior.  It  is  attached  by  one  extremity  to  the  front 
of  the  styloid  process  of  the  radius ;  by  the  other  extremity 
it  is  attached  to  the  pisiform  bone,  sending"  off  a  process 
which  becomes  attached  to  the  unciform  process  of  the  unci- 
form bone. 

The  Muscles  of  the  Forearm. 

The  muscles  of  the  forearm  are  divided  into  those  on  the 
front  and  those  on  the  back  ;  and  these  are  ag"ain  subdivided 
by  intermuscular  septa  into  a  superficial  and  deep  g"roup  on 
the  front  of  the  forearm,  and  into  three  g"roups — external  or 
radial,  superficial,  and  deep — on  the  back.  It  must  be  borne 
in  mind  that  every  muscle  found  upon  the  front  of  the  forearm 
is  to  produce  either  flexion  or  pronation  and  that  every  muscle 
upon  the  back  of  the  forearm  produces  either  extension  or 
supination.  Hence  the  names  of  the  muscles  upon  the  front 
will  be  €\\}\Q.x:  Flexor  o^  Pronator,  on  the  back  either  i5'.v/f^v^6^o?- 
or  Supinator',  and  to  these  names  are  added  the  particular 
function  of  the  muscle,  as  a  Plexor  of  the  radial  side  of  the 
carpus  or  an  Kxtensor  of  the  radial  side  of  the  carpus. 

The  Muscles  of  the  Front  of  the  Forearm. 

The  muscles  of  the  front  are  eig"ht  in  number  and  are  di- 
vided   into  two   layers,   of  which  the  superficial  contains  five 


246  DESCRIPTIVE  ANATOMY. 

muscles  and  the  deep  three.  The  superficial  muscles  on  the 
front  of  the  forearm  have  a  common  tendon,  the  orig-in  of  which 
tendon  is  from  the  inner  condyle  of  the  humerus,  the  investing 
fascia  which  covers  the  muscle,  and  the  intermuscular  septa 
which  are  sent  down  between  the  muscular  fibres.  In  addition 
to  this,  many  muscles  have  other  points  of  origin. 

Pronator  Radii  Teres. 

The  Pronator  Radii  Teres  is  the  first  muscle  of  the  super- 
ficial g-roup.  It  takes  its  origin  from  the  internal  condyle  o  f 
the  humerus,  from  the  investing  fascia  which  covers  it  and 
from  an  intermuscular  septum  between  itself  and  the  Flexor 
carpi  radialis.  In  addition  to  this,  there  is  a  small  head,  or 
deep  head,  of  this  muscle,  which  arises  from  the  inner  face  of 
the  coronoid  process  of  the  ulna,  these  two  heads  being  sep- 
arated by  the  median  nerve.  The  two  heads  unite  after  a  short 
course,  and  passing  downward  and  outward,  wind  around  the 
shaft  of  the  radius,  and  are  inserted  into  the  middle  one-third 
of  the  outer  surface  of  the  shaft  of  the  radius. 

Flexor  Carpi  Radialis. 

The  Flexor  Carpi  Radialis  is  the  second  muscle  of  the  su- 
perficial group.  It  arises  from  a  common  origin, — the  internal 
condyle  of  the  humerus  and  investing  fascia,  and  two  intermus- 
cular septa,  one  between  itself  and  the  Pronator  radii  teres 
and  the  other  between  itself  and  the  Palmaris  longus.  It  "is 
a  long  and  slender  muscle,  which  passes  downward,  with  a 
slight  inclination  outward  for  the  upper  one-third  of  the  fore- 
arm. The  muscular  belly  then  changes  into  a  tendon,  which 
running  vertically  downward,  passing  through  a  groove  in  the 
trapezium,  is  inserted  into  the  base  of  the  metacarpal  bone  of 

the  index  finger. 

Palmaris  Longus. 

The  Palmaris  Longus  arises  from  the  internal  condyle,  the 
investing  fascia,  and  the  intermuscular  septa,  between  itself  and 
the  Flexor  carpi  radialis  on  one  side  and  the  Flexor  sublimis 
digitorum  on  the  other.  It  is  a  small  and  very  slender  muscle, 
which  passing  straight  down  the  middle  of  the  front  of  the 


THE  MUSCULAR  SYSTEM.  247 

forearm,  soon  becomes  tendinous  and  is  inserted  into  the  pal- 
mar fascia  chiefly,  but  partly  into  the  anterior  annular  liga- 
ment. The  muscle  should  be  called  the  "middle  flexor  of  the 
carpus. 

Flexor  Carpi  Ulnaris. 

The  Flexor  Carpi  U/?iaris  a.r\ses  from  the  internal  condyle, 
the  investing-  fascia,  and  the  intermuscular  septa  between  itself 
and  the  Flexor  sublimisdigitorum.  It  also  arises  from  the  in- 
ner side  of  the  olecranon  process  and  from  the  upper  two-thirds 
of  the  posterior  border  of  the  ulna.  This  muscle  remains  fleshy 
until  within  two  inches  of  the  wrist  joint.  It  then  becomes 
tendinous  and  is  inserted  into  the  base  of  the  metacarpal  bone 
of  the  little  fing-er,  its  tendons  enclosing-  the  pisiform  as  a 
sesamoid  bone. 

Flexor  Sublimis  Digitorum. 

The  Flexor  Sublimis  Dig-itoruin  lies  beneath  the  preceding- 
muscles  of  the  g-roup  and  is  in  contact  with  the  investing-  fas- 
cia for  only  a  small  portion  of  its  course,  frequently  not  touch- 
ing- that  fascia  at  all.  It  arises  from  the  inner  condyle  of  the 
humerus,  from  the  internal  lateral  lig-ament  of  the  elbow, 
from  the  base  of  the  coronoid  process  of  the  ulna,  and  from 
the  oblique  line  of  the  radius  for  about  two-thirds  of  that  line. 
It  descends  beneath  the  superficial  layer  of  muscles,  and  at 
the  lower  third  of  the  forearm  divides  into  four  tendons. 
These  tendons,  enclosed  in  a  synovial  sheath,  enter  the  hand 
by  passing-  beneath  the  anterior  annular  lig-ament,  and  then, 
separating-  from  one  another,  pass  forward  to  each  fing-er,  to 
be  inserted  into  the  side  of  the  shaft  of  the  second  phalanx  of 
each  of  the  four  lesser  fing-ers.  At  the  base  of  the  first  pha- 
lanx, each  tendon  splits,  and  throug-h  this  opening-  the  tendon 
of  the  deep  Flexor  pisses.  The  superficial  tendons  then 
unite  and  form  a  g-roove,  in  which  the  tendon  of  the  deep 
Flexor  lies.  They  then  split  a  second  time  to  be  inserted 
into  the  sides  of  the  second  phalang-es. 

Second  or  Deep  Layer. 

Flexor  Profundus  Dig-itorum  Pronator  Quadratus 

Flexor  Long-US  Pollicis 


248  DESCRIPTIVE  ANATOMY. 

The  flexor  profundus  digitornm  lies  just  beneath  the  subli- 
mis  and  to  the  ulnar  side  of  the  lon^us  pollicis.  It  arises  from 
the  upper  two-thirds  of  the  anterior  and  inner  faces  of  the 
ulna  ;  by  a  strong-  aponeurosis  from,  the  posterior  border  of 
the  ulna,  where  it  blends  with  the  flexor  carpi  ulnaris,  and 
from  the  ulna  part  of  the  interosseous  membrane. 

It  divides  into  four  tendons,  which  enter  the  palm  of  the 
hand  and,  separating,  run  one  to  each  of  the  fingers,  pierce 
the  tendon  of  the  superficial  flexor  at  the  base  of  the  fingers, 
and  are  inserted  into  the  base  of  the  last  phalanx. 

Flexor  Longus  Pollicis. 

The  flexor  long-its  pollicis  lies  to  the  outer  side  of  the  preced- 
ing- muscle.  It  arises  from  about  the  middle  two  fourths  of 
the  front  of  the  radius  and  from  the  radial  side  of  the  interos- 
seous membrane.  It  passes  downward  and,  becoming  tendi- 
nous, runs  beneath  the  anterior  annular  ligament,  passes 
between  the  two  heads  of  the  flexor  brevis  pollicis  and  is 
inserted  into  the  base  of  the  last  phalanx  of  the  thumb. 

Pronator  Quadratus. 

The  pronator  quadratus  occupies  the  lower  fourth  of  the 
forearm  and  thus  prevents  the  origin  of  the  preceding  mus- 
cles for  that  distance.  It  arises  from  the  inner  side  of  the 
ulna,  receiving  some  fibres  from  the  front  of  that  bone  as  it 
passes  over  it,  and  is  inserted  into  the  front  of  the  radius  as 
far  as  the  outer  side. 

Nerve  and  Arterial  Supply. 

The  muscles  on  the  outer  side  of  the  forearm  are  supplied 
by  branches  from  the  radial  artery  ;  those  on  the  inner  side 
from  the  ulnar.  All  of  the  muscles  on  the  front  of  the  fore- 
arm are  supplied  by  the  median  nerve  or  one  of  its  branches, 
except  the  Flexor  carpi  ulnaris  and  one-half  of  the  Flexor 
profundis  digitorum.  The  branch  of  the  median  which  sup- 
plies the  deep  muscles  is  called  the  interosseous  ;  the  nerve 
supplying  the  Flexor  carpi  ulnaris  and  the  inner  half  of  the 
Flexor  profundus  digitorum  is  the  ulnar. 


THE  MUSCULAR  SYSTEM.  249 


Action  of  the  Muscles  of  the  Forearm. 

The  name  indicates  the  action  of  each  of  these  muscles,  but 
indicates  onl}'  a  portion  of  the  action. 

The  Pronator  radii  teres  is  first  a  pronator,  of  the  hand;  but 
after  having-  acted  to  its  fullest  extent  as  a  pronator,  it  then 
becomes,  in  common  with  the  other  muscles  of  the  g-roup,  a 
flexor  of  the  forearm  upon  the  arm. 

The  Flexor  carpi  radialis,  Pahnaris  loiigzis,  and  Plexor 
carpi  iiluaris  are  primarily  flexors  of  the  wrist;  but  the  pal- 
maris  long-us  in  addition  is  a  tensor  of  the  palmar  fascia, 
and  all  of  the  three  flex  the  forearm  upon  the  arm. 

The  Flexor  siiblimis  dig-itoruni  flexes  the  second  phalanx  on 
each  of  the  four  lesser  fing-ers.  Having*  effected  this,  it  will 
flex  the  first  phalanx  upon  the  hand;  continuing-  to  act,  it  flexes 
the  hand  upon  the  wrist;  and  acting-  still  further,  it  flexes  the 
forearm  upon  the  arm. 

The  Flexor  longus  -pollicis  flexes  the  first  phalanx  of  the 
thumb;  then  the  second  upon  the  metacarpal  bone  of  the 
thumb  ;  then  the  metacarpal  bone  upon  the  hand,  and  the 
hand  upon  the  wrist,  and  the  wrist  upon  the  forearm. 

The  Flexor  profundus  dig-itorum  flexes  the  first  phalanx 
upon  the  second;  but  cannot  do  this  until  a  superficial  flexor 
first  has  flexed  the  second.  Continuing-  its  action,  it  will  act 
in  concert  with  and  like  the  superficial  flexor. 

Interosseous  Membrane. 

The  interosseous  membrane,  mentioned  above,  is  a  strong- 
fibrous  membrane  stretched  l)etween  the  two  bones.  It  econo- 
mizes weig-ht,  while  it  furnishes  as  stable  an  orig-in  for  mus- 
cles as  does  bone. 

Posterior  Region. 

The  muscles  upon  the  back  of  the  forearm  also  have  a  com- 
mon origin,  viz  :  external  condyle  of  humerus,  investing-  fascia 
and  intermuscular  septa. 

They  are  divided  into  three  g-roups,  each  containing-  four 
muscles,  called  radial,  superficial  and  deep  g-roups.     These 


250  DESCRIPTIVE  ANATOMY. 

muscles,  are  either  extensors  or  supinators,,  acting-  in  opposi- 
tion to  those  on  the  front  of  the  forearm. 

Radial  Group. 

Supinator  Long-us  Extensor  Carpi  Radialis 

Extensor  Carpi  Radialis  Longior 

Brevior  Supinator  Brevis 

Supinator  Longus. 

The  supinator  longus  derives  its  name  from  the  facts  that 
it  is  a  supinator  of  the  forearm  and  that  there  is  another 
supinator  called  brevis. 

It  arises  from  the  upper  two-thirds  of  the  external  condy- 
loid ridg"e  and  from  the  external  inter-muscular  septum,  and, 
after  descending-  about  two-thirds  of  its  course,  terminates 
in  a  tendon  which  is  inserted  into  the  outer  side  of  the  base 
of  the  styloid  process  of  the  radius. 

Extensor  Carpi  Radialis  Longior. 

The  extensor  carpi  radialis  long-ior  derives  its  name  from 
the  action  of  the  muscle  and  from  the  fact  that  there  is  another 
radial  extensor  which  is  shorter.  It  arises  from  the  lower 
one-third  of  external  condyloid  ridge  and  from  the  external 
inter-muscular  septum,  and  descends  to  be  inserted  by  its 
tendon  into  the  base  of  the  metacarpal  bone  of  the  index 
finger. 

Extensor  Carpi  Radialis  Brevior. 

The  extensor  carpi  radialis  brevior^  deriving"  its  name  from 
the  facts  stated  with  the  preceding-  muscle,  arises  from  the 
common  origin,  which  is  the  external  condyle,  the  investing- 
fascia  and  an  inter-muscular  septum  bet^veen  itself  and  the 
extensor  communis  digitorum.  It  passes  downward,  between 
the  extensor  carpi  radialis  longior  and  the  extensor  communis 
digitorum,  crosses  beneath  the  tendons  of  the  extensor  ossis. 
metacarpi  pollicis  and  extensor  primii  internadii  poUicis,  as 
does  the  preceding  muscle,  before  reaching-  the  posterior 
annular  ligament,  then  passes  beneath  the  tendon  of  the  exten- 
sor secundi  internodii  pollicis  and  is  inserted  into  the  radial 


THE  MUSCULAR  SYSTEM.  251 

side  of  the  base  of  the  third  metacarpal  bone.  This  muscle 
and  the  extensor  carpi  radialis  longior,  lie  in  the  same  groove 
while  passing  under  the  annular  ligament. 

Supinator  Brevis. 

The  siifiinator  brevis  is  a  thin  flat  muscle  which  encircles 
the  upper  third  of  the  radius. 

It  arises  from  the  external  condyle  of  the  humerus,  the 
external  lateral  and  orbicular  ligaments  from  the  triangular 
depressed  surface  beneath  the  lesser  sigmoid  cavity  of  the 
ulna,  and  to  some  extent  from  the  intermuscular  septum 
between  the  deep  and  superficial  groups.  It  winds  around 
the  radius  and  is  inserted  into  the  upper  third  of  its  oblique 

ridge. 

Back  of  Forearm— Superficial  Group. 

Extensor  Communis  Digitorum.  Extensor  Carpi  Ulnaris. 

Extensor  Minimi  Digiti.  Anconeus. 

Extensor  Communis  Digitorum. 

The  extensor  communis  digitorum  derives  its  name  from 
its  action  as  the  extensor  common  to  the  four  fingers.  It 
arises  from  the  common  origin,  external  condyle  investing 
fascia  and  two  inter-muscular  septa;  one  between  itself  and 
the  extensor  carpi  radialis  brevior  externally,  and  one  between 
itself  and  the  extensor  minimi  digiti,  internally.  Passing 
down  the  back  of  the  forearm  the  muscle  divides  into  three 
tendons,  which  pass  beneath  the  annular  ligament  in  a  com- 
partment with  the  extensor  indicis.  On  reaching  the  back  of 
the  hand  the  innermost  tendon  divides  into  two ;  and  the  four 
tendons,  thus  formed,  pass  to  the  four  lesser  fingers  and  are 
inserted  into  the  backs  of  the  four  lesser  fingers  after  the 
manner  of  extensor  iendo?is.  This  expression  means  that 
opposite  the  metacarpo-phalangeal  joint  each  tendon  becomes 
narrower  and  receives  the  tendon  of  the  lumbricales.  Pass- 
ing to  the  shaft,  each  tendon  becomes  broader  and  thinner. 
Upon  reaching  the  phalangeal  joints  each  becomes  thicker 
and  furnishes  a  posterior  ligament  for  those  joints.  The 
tendon  to  the  ring  finger  is  usually  bound  by  a  slight  band  to 
the  tendons  of  the  little  and  middle  fincrers. 


252  DESCRIPTIVE  ANATOMY. 

Extensor  Minimi  Digiti. 

The  extensor  ininimi  digiti  is  an  offshoot  of  the  common 
extensor  and,  as  its  name  indicates,  has  for  its  function  the 
extension  of  the  little  fing-er.  It  arises  from  the  common  origin 
(external  condyle,  investing-  fascia  and  septa  between  itself 
and  the  extensor  communis  externally  and  the  extensor  carpi 
ulnaris  internally)  and  is  inserted  into  the  whole  leng"th  of  the 
back  of  the  little  fing-er  along"  with  the  slip  furnished  that 
fing-er  by  the  common  extensor,  after  the  manner  of  extensor 
tendons. 

This  muscle  is  really  an  offshoot  of  the  common  extensor. 
Its  claim  to  individuality  is  that  it  has  a  separate  compartment 
in  the  annular  ligament. 

Extensor  Carpi  Ulnaris. 

The  extensor  carpi  ulnaris  derives  its  name  from  its  action 
as  an  extensor  of  the  hand  and  from  its  situation  on  the  ulnar 
side  of  the  forearm.  It  arises  from  the  common  origin  (exter- 
nal condyle,  investing  fascia  and  the  intermusular  septa 
between  itself  and  the  extensor  minimi  dig-iti  externally 
and  the  deep  g-roup  in  front)  and,  by  a  strong-  aponeurosis, 
which  blends  with  that  g-iving-  origin  to  the  carpal  flexor,  from 
the  middle  third  of  the  posterior  border  of  the  ulna.  The 
muscle  remains  fleshy  until  just  above  the  wrist  joint  when  it 
becomes  tendinous  and,  passing-  through  a  groove  on  the  back 
of  the  styloid  process  of  the  ulna,  in  its  own  compartment  in 
the  annular  ligament,  is  inserted  into  the  base  of  the  metacar- 
pal bone  of  the  little  fing-er  on  its  ulnar  side. 

Anconeus. 

The  anconeus  is  a  small  triangular  muscle  which  arises  by 
its  apex  from  the  external  condyle  of  the  humerus,  and  is 
inserted  by  its  base  into  the  olecranon  process  and  triangular 
surface  at  the  upper  extremity  of  the  ulna.  It  is  really  an 
offshoot  of  the  triceps  extensor,  and  its  action  is  to  aid  that 
muscle  in  extending  the  forearm  on  the  arm. 


THE  MUSCULAR  SYSTEM.  253 

Deep  Group. 

The  four  muscles  of  this  group  lie  beneath  those  of  the 
superficial  g-roup,  and  all  arise  from  the  interosseous  mem- 
brane as  one  attachment.  As  indicated  b}^  their  names,  they 
are  all  extensors,  three  being-  appropriated  by  the  thumb  and 
one  by  the  index  fing-er. 

Kxtensor  Ossis  Meta-  Extensor  Primi  Inter' 
carpi  PoUicis  nodii  Pollicis 

Extensor  Secundi  Inter- 

nodii  Pollicis  Extensor  Indicis 

Extensor  Ossis  Metacarpi  Pollicis. 

The  extensor  ossis  metacarpi  pollicis  arises  from  the  radius, 
ulna,  interosseous  membrane  and  a  fibrous  septum  between  it 
and  the  extensor  primi.  Its  upper  attachment  to  both  bones 
is  limited  by  the  supinator  brevis.  It  becomes  tendinous  and 
winding"  around  the  radius  crossing-  the  tendons  of  the  exten- 
sor carpi  radialis  lang-ior  and  brevior,  and  passing-  throug-h 
the  annular  lig-ament,  is  inserted  into  the  base  of  the  metacar- 
pal bone  of  the  thumb. 

Extensor  Primi  Internodii  Pollicis. 

The  extensor  primi  internodii  pollicis  arises  from  the  radius 
for  about  its  middle  two  fourths  and  interosseous  membrane. 
After  becoming-  tendinous  it  follows  the  extensor  ossis  meta- 
carpi pollicis,  lying"  internal  to  that  muscle,  crosses  the  same 
tendons,  passes  throug-h  the  same  groove  on  the  radius  and  is 
inserted  into  the  base  of  the  first  phalanx  of  the  thumb. 

Extensor  Secundi  Internodii  Pollicis. 

The  extensor  secundi  internodii  pollicis  arises  from  the  ulna 
for  about  its  middle  third  and  from  the  interosseous  membrane. 
Its  tendon  passes  throug"h  a  separate  compartment  in  the 
annular  lig-ament,  crosses  the  tendons  of  the  extensor  carpi 
radialis  lang-ior  and  brevior  after  passing-  throug-h  the  annular 
lig-ament,  and  is  inserted  into  the  base  of  the  last  phalanx  of 
the  thumb. 


254  DESCRIPTIVE  ANATOMY. 

Extensor  Indicis. 

The  extensor  indicis  arises  from  the  tilna  and  interosseous 
membrane  and  is  inserted  into  the  whole  leng-th  of  the  back  of 
the  index  fing-er,  blending-  with  the  tendon  furnished  that  fin- 
ger by  the  common  extensor.  It  passes  through  the  annular 
ligament  in  a  compartment  common  to  it  and  the  extensor 
communis  digitorum. 

Action — The  names  of  these  muscles  in  a  large  measure 
indicate  their  action.  A  carpal  extensor  extends  the  hand  and 
draws  it  to  its  own  side.  The  radial  and  ulnar  extensors, 
acting  together,  bend  the  hand  straight  backward.  The 
extensors  of  the  fingers  bend  the  fingers  backward  and  then 
extend  the  hand  at  the  wrist.  Of  the  supinators,  the  brevis 
is  the  stronger.  It  is  only  when  the  hand  is  in  full  supination 
that  the  supinator  longus  acts  to  produce  supination.  With 
the  hand  in  full  supination  it  becomes  a  pronator.  It  may 
also  act  as  a  flexor  of  the  forearm  upon  the  arm. 

The  supinator  longus  and  extensor  carpi  radialis  langior 
are  supplied  by  the  musculo-spiral  nerve  ;  the  others  by  the 
posterior  interosseous. 

The  Muscles  of  the  Hand. 

The  central  portion  of  the  palm  of  the  hand  is  depressed 
below  the  level  of  a  prominence  on  either  side,  one,  extending 
from  the  base  of  the  little  finger  toward  the  wrist,  called  the 
hypothenar  eminence,  and  the  other,  considerably  more 
prominent,  extending  upward  from  the  base  of  the  first  phalanx 
of  the  thumb  toward  the  wrist,  called  the  thenar  eminence. 

When  the  skin  has  been  removed  a  thick  layer  of  fatty 
tissue  is  exposed,  which  serves  as  a  protection  for  the  vessels 
and  nerves  in  grasping  with  the  hand  ;  and  beneath  this  is  a 
strong  fascia  called  the  palmar  fascia.  It  has  a  thick  central 
portion  and  two  thinner  lateral  portions  which  cover  the 
muscles  forming  the  thenar  and  hypothenar  eminences. 
Tracing  this  fascia  to  the  wrist,  it  is  found  to  be  continuous 
with  a  strong   fibrous  band   which  extends  across  the  wrist 


THE  MUSCULAR  SYSTEM.  255 

from  one  side  to  the    other,  binding-  down  the  tendons  which 
pass  beneath  it,  known  as  the  anterior  annular  ligament. 

The  muscles  of  the  hand  consist  of  two  groups,  the  thenar 
and  hj^pothenar  groups,  and  four  small  muscles  found  in  the 
depressed  portion  of  the  hand,  called  lumbricales. 

Thenar  Group. 

The  muscles  of  the  thenar  group  are  appropriated  to  the 
thumb,  the  movements  of  which  are  as  follows  :  {a)  Abduction, 
or  movement  of  the  thumb  outward  from  the  index  finger, 
{b)  Adduction,  a  movement  in  the  opposite  direction. 
{d)  Flexion,  in  which  the  thumb  is  put  in  contact  with  the 
palp  of  any  of  the  fingers.  This  is  effected  by  putting  in 
motion  the  metacarpal  bone  of  the  thumb  by  a  muscle  called 
opponens.  {c)  Extension,  movement  in  the  opposite  direction 
effected  by  muscles  on  the  back  of  the  forearm,  which  have 
been  described. 

Abductor  Pollicis  Flexor  Ossis  Metacarpi  Pollicis. 

Flexor  Brevis  Pollicis  Adductor  Pollicis. 

Abductor  Pollicis. 

The  abductor  pollicis  arises  from  the  trapezium  bone  and 
anterior  annular  ligament,  and  is  inserted.  In  the  outer  side 
of  the  base  of  the  first  phalanx  of  the  thumb. 

The  flexor  of  the  metacarpal  bone  of  the  thumb,  or  the 
opponens  pollicis,  arises  from  the  trapezium  bone  and  anterior 
annular  ligament,  and  is  inserted  into  the  whole  length  of  the 
radial  border  of  the  metacarpal  bone  of  the  thumb. 

Flexor  Brevis  Pollicis. 

The  flexor  brevis  pollicis  consists  of  two  parts,  one  of 
which,  the  superficial  portion,  arises  from  the  trapezium  bone 
and  annular  ligament,  and  the  other,  or  deep  portion,  from 
the  trapezoid,  os  magnum  and  base  of  the  metacarpal  bone  of 
the  middle  finger.  It  Is  inserted  into  both  sides  of  the  base 
of  the  first  phalanx  of  the  thumb,  its  tendons  of  insertion  hav- 
ing sesamoid  bones  in  them. 


256  DESCRIPTIVE  ANATOMY. 

Abductor  Pollicis. 

The  adductor  -pollicis  is  a  flat  triangular  muscle  which 
arises  by  its  base  from  the  whole  length  of  the  front  of  the 
metacarpal  bone  of  the  middle  finger.  It  is  inserted  into  the 
inner  side  of  the  base  of  the  first  phalanx  of  the  thumb. 

Hypothenar  Group. 

Palmaris  Brevis  Abductor  Minimi  Digiti 

Flexor  Brevis  Minimi  Digiti  Adductor  Ossis  Metacarpi 

Minimi  Digiti 
Palmaris  Brevis. 

The  palmaris  brevis  is  a  small  pale  muscle  lying  just  beneath 
the  skin  of  the  palm.  It  arises  from  the  palmar  fascia  and  the 
anterior  annular  ligament,  and  passing  inward,  about  an  inch 
wide,  is  inserted  into  the  skin  on  the  inner  border  of  the  hand. 

Abductor  Minimi  Digiti. 

The  abductor  minimi  digiti  arises  from  the  pisiform  bone 
and  is  inserted  into  the  inner  side  of  the  base  of  the  first 
phalanx  of  the  little  finger. 

Action — It  is  an  abductor  of  the  little  finger,  /.  e.,  draws 
the  little  finger  inward  away  from  the  ring  finger. 

Flexor  Brevis  Minimi  Digiti. 

The  flexor  brevis  minimi  digiti  arises  from  the  unciform 
process,  of  the  unciform  bone  and  the  anterior  annular 
ligament,  and  is  inserted  into  the  base  of  the  first  phalanx  of 
the  little  finger. 

Action — It  is  a  flexor  of  the  little  finger. 

Adductor  Ossis  Metacarpi  Minimi  Digiti. 

The  adductor  ossis  metacarpi  minimi  digiti  arises  from  the 
unciform  process  of  the  unciform  bone  and  the  anterior  annular 
ligament,  and  is  inserted  into  the  whole  length  of  the  meta- 
carpal bone  of  the  little  finger. 

Action — It  draws  the  metacarpal  bone  of  the  little  finger 
outward  and  forward,  carrying  the  little  finger  towards  the 
thumb. 


THE  MUSCULAR  SYSTEM.  257 

Flexor  Tendons  of  the  Fingers. 

It  has  been  seen  that  the  tendons  of  the  flexor  sublimis 
dig-itorum  split  at  the  base  of  the  fing-ers  to  allow  the  passage 
of  the  tendons  of  the  flexor  profundus,  unite  and  again  split 
to  be  inserted  into  the  sides  of  the  shaft  of  the  second  phalanx 
of  each  finger.  Before  its  insertion  each  tendon  gives  off 
thread-like  prolongations,  called  vincula  accessoria,  which  are 
inserted  into  the  sides  of  the  bones  ;  and  both  tendons  are  bound 
down  to  the  bones  by  transverse  bands  of  ligamentous  fibres 
called  the  thecal. 

Muscles  of  the  Lower  Extremity. 

The  muscles  of  the  lower  extremity  are  divided  into  those 
of  the  hip,  thigh,  leg  and  foot.  The  hip  is  called  the  gluteal 
region. 

Gluteal  Region. 

As  in  the  upper  extremity,  the  muscles  are  here  covered  by 
an  investing  fascia,  which  is  much  thicker  and  stronger  than 
in  the  former  situation,  known  in  the  thigh  as  the  fascia  lata 
or  vagina  femoris. 

The  muscles  of  the  gluteal  region,  nine  in  number,  are  ar- 
ranged in  three  layers,  each  of  which  has  a  muscle  called 
gluteus. 

It  receives  its  nerve  supply  from  the  lesser  sciatic. 

First  Layer. 
Gluteus  Maximus. 

T\\Q.  g-luteus  maxhmis  is  a  quadrilateral  muscle,  the  largest 
and  coarsest  in  the  body,  and  forms  the  bulge  of  the  buttock. 
It  arises  from  the  posterior  fifth  of  the  crest  of  the  ilium, 
from  the  dorsum  ilii  between  the  superior  curved  line  and  the 
crest,  from  the  posterior  portion  of  the  crest,  from  the  poste- 
rior surface  of  the  sacrum  and  coccyx,  from  the  greater  sacro- 
sciatic  ligament  and  from  the  fascia  covering  the  gluteus 
medius.  It  passes  obliquely  downward  and  outward  to  be 
inserted  into  the  line  leading  from  the  trochanter  major  to  the 
linea  aspera  and  into  the  fascia  lata. 

Des  Anat— 17 


258  DESCRIPTIVE  ANATOMY. 

Action — It  is  an  abductor  and  outward  rotator  of  the  thig-h, 
a  tensor  of  the  fascia  lata  and  steadies  the  pelvis  on  the  femur. 

Second  Layer. 

Gluteus  Medius  Gemellus  Inferior 

Pyriformis  Obturator  Internus 

Gemellus  Superior  Quadratus  Femoris 

Gluteus  Medius. 

The  g-luteus  inedhis  is  partially  covered  by  the  g-luteus 
maximus.  It  arises  from  the  anterior  four-fifths  of  the  crest 
of  the  ilium,  from  the  dorsum  ilii  between  the  middle  curved 
line  and  the  crest  and  from  the  investing-  fascia,  which  covers 
its  outer  front  part.  It  is  inserted  into  the  outer  part  of  the 
trochanter  major.  On  its  outer  edg^e  the  muscle  is  continuous 
with  the  g-luteus  maximus. 

Action — Its  g-reatest  power  is  shown  in  abduction  ;  but  its 
anterior  fibres  can  rotate  the  femur  inward  while  the  posterior 
rotate  it  outward.  It  can  twist  the  pelvis  on  the  femur,  draw- 
ing- the  body  to  that  side.  It  steadies  the  pelvis  on  the  femur 
and  can  draw  the  limb  forward  in  walking-. 

It  is  supplied  by  the  superior  g-luteal  nerve. 

Pyriformis. 

The  j;)yriformis  is  a  pear-shaped  muscle.  It  arises  within 
the  pelvis  by  three  fleshy  slips  interposed  between  the  ante- 
rior sacral  foramina  from  the  first  to  the  fourth  and  from  the 
adjoining-  part  of  the  ilium.  It  escapes  from  the  pelvis 
throug-h  the  g-reater  sacro-sciatic  foramen,  passes  downward 
and  outward,  and  is  inserted  into  the  posterior  border  of  the 
upper  extremity  of  the  trochanter  major,  or  into  the  dig-ital 
pit. 

Action — It  is  an  external  rotator  of  the  thigfh. 

The  Gemelli. 

The  gemelli  are  a  pair  of  small  muscles  lying-  one  above 
and  the  other   below  the   tendon  of  the  obturator    internus. 

^h.Q  §emullu^  superior  arises  from  the  spine  of  the  ischium, 
runs  horizontally  outward  and  is  inserted  into  the  digital  pit 
of  the  trochanter  major. 


THE  MUSCULAR  SYSTEM.  259 

The  gemellus  inferior  arises  from  the  tuberosit}^  of  the 
ischium,  passes  horizontally  outward  and  is  inserted  into  the 
digfital  fossa. 

Action — Both  are  outward  rotators  of  the  thigh. 

Obturator  Internus. 

The  obturator  internus  arises  within  the  pelvis  from  the 
inner  surface  of  the  obturator  membrane,  from  the  margin  of 
the  obturator  foramen  and  from  the  inclined  plane  of  the 
ischium.  Its  course  is  downward  and  slightly  backward 
until,  becoming  tendinous,  it  escapes  from  the  pelvis  through 
the  lesser  sacro-sciatic  foramen,  and  passing  horizontally,  out- 
ward, its  tendon  winding  around  the  posterior  border  of  the 
ischium  just  below  the  spine,  it  is  inserted  into  the  digital 
fossa  of  the  trochanter  major. 

Action — It  is  an  outward  rotator  of  the  thigh. 

duadratus  Femoris. 

The  quadratus  femoris^  as  its  name  indicates,  is  a  square 
muscle  which  lies  below  the  tendon  of  the  obturator  internus. 
It  arises  from  the  outer  lip  of  the  tuberosity  of  the  ischium, 
and  is  inserted  across  the  posterior  inter-trochanteric  line. 
Its  insertion  is  rarely  marked  by  the  presence  of  the  linea 
quad  rati. 

Action — It  is  an  outward    rotator  of  the   femur.     These 

muscles  are  all   supplied   by  branches  coming  directly  from 

the  sacral  plexus. 

Third  Layer. 

Gluteus  Minimus  Obturator  Externus 

Gluteus  Minimus. 

The  g'luteus  ini7iimus  lies  beneath  the  gluteus  medius  and 
maximus.  It  is  a  triangular  radiated  muscle  which  arises 
from  the  dorsum  ilii  between  the  middle  and  inferior  curved 
lines.  It  passes  down,  narrowing  as  it  descends,  and  is 
inserted  into  the  anterior  border  of  the  trochanter  major.  In 
front,  it  is  continuous  with  the  gluteus  medius. 

Action — It  is  an  abductor  and  invjard  rotator  of  the  thigh. 
Acting  from  below  it  steadies  the  pelvis  on  the  femur. 

It  is  supplied  by  the  superior  gluteal. 


260  DESCRIPTIVE  ANATOMY. 


Obturator  Externus. 

The  obturator  externus  arises  from  the  inner  two-thirds  of 
the  outer  surface  of  the  obturator  foramen  and  from  the  inner 
margin  of  the  obturator  foramen.  It  narrows  to  a  tendon, 
which,  passing-  outward  behind  the  neck  of  the  femur,  is  in- 
serted into  the  digital  pit  of  the  trochanter  major.  It  lies  on 
the  capsular  ligament  of  the  hip-joint. 

Action — It  is  an  external  rotator  of  the  thigh. 

It  is  supplied  by  the  obturator  nerve. 

Femoral  Region. 

The  muscles  of  the  thigh  are  arranged  in  four  groups,  viz: 
posterior,  superficial,  anterior  and  internal  femoral  groups. 
Investing  the  thigh,  just  beneath  the  skin  and  superficial  fascia, 
is  a  strong  ,  thick,  fibrous  membrane  which  descending  to  the 
knee,  invests  that  joint  and  passes  on  to  become  the  invest- 
ing fascia  of  the  leg.  From  the  hip  to  the  knee  it  is  known  by 
three  names,  investing  fascia  of  the  thigh,  vagina  femoris,  or, 
generally,  fascia  lata.  It  not  only  forms  a  firm  resisting  cov- 
ering for  the  muscles,  but  sends  in  septa  between  the  groups. 
Two  of  these  septa,  attached  to  the  lips  of  the  linea  aspera,  are 
known  respectively  as  the  external  and  internal  intermuscular 
septa.  The  external  intermuscular  septum  lies  between  the 
anterior  and  posterior  femoral  groups,  and  gives  origin  to 
muscles  of  both  groups.  The  internal,  lies  between  the  an- 
terior and  internal  groups,  no  septum  being  interposed  between 
the  internal  and  posterior  groups.  Above,  this  fascia  is  con- 
tinuous, on  the  front  of  the  thigh,  with  Pouparts  ligament, 
externally  and  posteriorly  with  the  fascia  covering  the  gluteal 
muscles,  while  internally  it  is  attached  to  the  tuberosity  of  the 
ischium  and  to  the  ischio  pubic  rami.  Below  it  seizes  the  bony 
prominences  around  the  knee  joint  and  becomes,  posteriorly, 
th.t  popliteal  fascia,  which  covers  in  the  popliteal  space. 

^  The  fascia  lata  consists  of  layers  between  which  are  found 
three  muscles  of  the  thigh  forming  the  superficial  femoral 
group. 


THE  MUSCULAR  SYSTEM.  261 

Where  the  fascia  covers  the  posterior  femoral  region  it 
is  thinner  than  in  any  portion  of  its  course. 

Posterior  Femoral  Region. 

Biceps  Flexor  Cruris  Semitendinosus 

Semimembranosus 

Biceps  Flexor  Cruris. 

The  biceps,  as  its  name  imports,  arises  by  two  heads. 
The  long  head  springs,  in  common  with  the  semitendinosus, 
from  the  tuberosity  of  the  ischium  and  descends  adherent  to 
the  semitendinosus  for  several  inches.  In  then  accompanies 
the  semitendinosus,  but  no  longer  adherent  to  it,  to  the  lower 
third  of  the  thigh;  is  joined  by  the  short  head  which  arises 
from  the  ijhole  length  of  the  outer  lip  of  the  body  of  the  linea 
aspera  and  from  the  external  intermuscular  septum.  The 
muscle  thus  formed  after  descending  to  the  lower  third  of  the 
femur  in  contact  with  the  semitendinosus,  leaves  that  muscle 
and  makes  for  the  outer  side  of  the  knee  joint,  where  it  is  in- 
serted chiefly  into  the  head  of  the  fibula,  but  sends  some  fibres 
to  the  outer  tuberosity  of  the  tibia  and  to  the  fascia  of  the  leg. 

Semitendinosus. 

The  semitendinosiLS  arises  in  common  with  the  long  head  of 
the  biceps,  adheres  to  it  for  several  inches  and  then  descends 
in  contact  with  it  to  the  lower  third  of  the  thigh  where  it  leaves 
the  biceps  and  passes  to  the  inner  aspect  of  the  knee-joint 
where  it  is  inserted  into  the  inner  surface  of  the  shaft  of  the 
tibia,  below  the  inner  tuberosity  sending  a  slip  to  the  fascia  of 
the  leg.  This  is  known  as  the  "'g-oose./oot'"  insertion.  It  is 
made  up  of  three  muscles,  viz:  semitendinous,  sartorius  and 
gracilis. 

Semimembranosus. 

The  semimenibranosiLs  arises  from  the  tuberosity  of  the 
ischium  just  in  front  of  and  external  to  the  preceding  muscles 
and  descends,  in  company  with  them,  to  the  lower  third  of  the 
femur,  whence  it  accompanies  the  semitendinous  to  the  inner 
side  of  the   knee-joint  and  receives  a  three-fold   insertion,  viz: 


262  DESCRIPTIVE  ANATOMY. 

into  the  Horizontal  groove  on  the  inner  tuberosity  of  the  tibia, 
into  the  j^ofliteal  fascia  and  into  the  posterior  lig-ament  of  the 
knee-joint. 

These  three  muscles  are  spoken  of  as  the  hamstring-  muscles, 
the  biceps  being"  the  outer,  the  semimembranous  and  semiten- 
dinosus  being-  the  inner. 

Action — It  will  be  seen  that  these  three  muscles  all  pass  over 
two  joints.  They  are,  of  course,  all  flexors  of  the  leg-  upon 
the  thig-h;  but,  in  addition,  the  biceps  has  a  slig-ht  influence  in 
rotating-  the  leg-  outward  and  the  others  in  rotating-  it  inward. 
After  flexing-  the  leg-  upon  the  thig-h,  they  can  then  extend  the 
thig-h  upon  the  pelvis.  When  acting-  from  below  they  draw 
the  pelvis  downward  and  backward,  keeping-  the  body  from 
falling-  forward,  or  aid  in  restoring  it  to  the  erect  posture  after 
stooping-. 

The  g-reat  siatic  nerve  supplies  the  g-roup. 

Superficial  Femoral  Group. 

Tensor  Vag-inae  Femoris  Gracilis  Sartorius 

Tensor  Vaginas  Femoris. 

The  tensor  vag-incB  femoris  is  a  short  flat  muscle  found  lying- 
on  the  outer  aspect  of  the  thig-h  between  the  two  layers  of  the 
fascia  lata.  It  arises  from  the  outer  lip  of  the  crest  of  the 
ilium  near  the  anterior  superior  spinous  process,  descends 
with  an  inclination  backward  and  is  inserted  into  the  fascia 
lata  about  one-fourth  down  the  thig-h. 

Action — It  is  a  tensor  of  the  fascia  lata  and  aids  in  rotating- 
the  limb  inward. 

Sartorius. 

The  sartoi'ius  is  the  long-est  muscle  in  the  body.  It  arises 
from  the  anterior  superior  spinous  process  of  the  ilium  and 
half  the  notch  below,  passes  obliquely  downward  and  inward 
across  the  upper  third  of  the  thig-h,  descends  vertically  behind 
the  internal  condyle  of  the  femur  and  then  turns  obliquely  for- 
ward to  be  inserted  into  the  upper  inner  face  of  the  tibia  below 
the  internal  tuberosity,  sending-  a  slip  to  the  fascia  of  the  leg-. 
It  forms  one  of  the  elements  of  the  "goose  foot"  insertion,  the 


THE  MUSCULAR  SYSTEM.  263 

other  two  being-  the  semitendinous  and  gracilis.  The  sartorius 
is  the  most  superficial  at  the  insertion,  then  the  gracilis  and 
the  semitendinosus  is  the  deepest. 

Action — It  flexes  the  thigh  on  the  pelvis,  the  leg"  on  the 
thig-h  and  carries  it  inward  across  its  fellow.  It  may,  acting- 
from  below,  twist  the  pelvis  so  as  to  carry  the  front  of  the 
body  towards  the  opposite  side. 

Gracilis. 

The  gracilis  arises  by  a  thin  broad  aponeurosis  from  the 
edg-e  of  the  symphysis  pubis  and  from  the  margin  of  the  ischio- 
pubic-ramus.  It  soon  becomes  fleshy  and  passes  down  the 
inner  aspect  of  the  thigh  to  be  inserted  into  the  upper  inner 
part  of  the  tibia,  below  the  inner  tuberosity,  sending  a  slip  to 
the  facia  of  the  leg,  /.  e.,  it  is  an  element  of  the  "goose  foot" 
insertion. 

Action — It  flexes  the  leg  on  the  thigh  and  aids  in  adducting 
the  thigh. 

The  tensor  vaginae  femoris  is  supplied  by  the  superior  glu- 
teal nerve  ;  the  sartorius  by  the  middle  cutaneous  ;  the  gracilis 
by  the  obturator. 

Anterior  Femoral  Region. 
Psoas  Magnus  Vastus  Externus 

Iliacus  Internus  Vastus  Internus 

Rectus  Femoris. 

The  muscles  in  this  region  are  usually  described  as  five  but 
can  very  readily  be  considered  as  two,  viz  :  Biceps  flexor 
femoris,  consisting  of  psoas  magnus  and  iliacus  internus  and 
the  triceps  extensor  cruris  consisting  of  rectus  femoris,  vas- 
tus internus,  and  vastus  externus.  The  last  three  are  inserted 
by  a  common  tendon,  called  the  ligamentum  patellai,  into  the 
anterior  tubercle  of  the  tibia,  their  action  being  transmitted 
through  the  patella  to  which  they  are  attached. 

As  might  be  inferred  from  their  action  they  all  arise  from 
some  point  perpendicular  to  their  insertion. 

Psoas  Magnus. 
The  -psoas  mag-nus  is  a  long  spindle  shaped  muscle  lying 
beside  the   vertebral   column  and  descending  into  the   thigh. 


264  DESCRIPTIVE  ANATOMY. 

It  arises  from  the  bodies  and  bases  of  the  transverse  processes 
of  the  last  dorsal,  and  all  the  lumbar  vertebra  ;  from  the 
intervertebral  disks  between  them  and  from  tendinous  arches 
attached  to  the  bodies  of  the  vertebrae,  extending-  from  the 
upper  lipped  edg-e  to  the  similar  lower  edge  of  each  vertebra, 
thus  leaving-  between  it  and  the  central  constricted  portion  of 
the  vertebra  an  interval  through  which  vessels  and  nerves  pass. 
The  muscle  descends  beside  the  vertebral  column  to  the  pel- 
vis and,  as  it  pass  beneath  Poupart's  lig-ament,  is  joined  by 
the  iliacus  internus  and  their  blended  tendon  is  inserted  into 
the  trochanter  minor  of  the  femur  and  the  bone  for  an  inch 
below. 

Iliacus  Internns. 

The  iliacus  internus  arises  from  the  whole  of  the  iliac  fossa, 
from  the  internal  lip  of  the  crest  of  the  ilium,  from  the  ante- 
rior superior  spinous  process  backward,  from  the  base  of  the 
sacrum,  from  the  ilio-lumbar  ligament  and  by  a  few  fibres 
from  the  capsular  ligament  of  the  hip  joint. 

The  fibres  converge  to  a  tendon  which,  passing  beneath 
Poupart's  ligament,  blends  wnth  that  of  the  psoas  magnus  to 
be  inserted  into  the  lesser  trochanter  of  the  femur  and  the 
bone  for  an  inch  below. 

Action — Primarily  these  muscles  are  flexors  of  the  thigh  on 
the  pelvis.  Owing  to  the  winding  of  the  tendon  around  the 
femur,  they  are  powerful  outward  rotators,  acting  just  as  the 
biceps  does  on  the  radius.  With  their  fixed  point  below,  and 
the  muscles  of  both  sides  acting,  they  bend  the  body  directly 
forward  ;  but  if  the  iliacus  of  one  side  acts  alone,  it  flexes  the 
pelvis  and  turns  the  body  to  the  opposite  side. 

The  psoas  is  supplied  by  branches  of  the  lumbar  plexus,  the 
iliacus  by  the  anterior  crural. 

Rectus  Femoris. 

The  rectus  femoris  derives  its  name  from  the  straightness 
of  its  course.  It  arises  by  a  forked  tendon,  one  fork  springing 
from  the  anterior  inferior  spinous  process  of  the  ilium,  the 
other  from  the  upper  margin  of  the  acetabulum.  The  two 
soon  unite,  and  the  tendon  thus  formed  after  a  short  course 


THE  MUSCULAR  SYSTEM.  265 

terminates  in  the  belly  of  the  muscle ;  and  that  in  turn 
terminates  at  the  lower  part  of  the  thig-h  in  a  strong-  tendon, 
which  is  inserted  into  the  upper  end  of  the  patella.  The 
fibres  of  this  muscle  have  a  bipenniform  arrangfement. 

Vastus  Externus. 

The  vastus  externus  arises  from  the  base  of  the  trochanter 
major,  from  the  line  leading-  from  the  trochanter  major  to  the 
linea  aspera,  from  the  upper  half  or  third  of  the  outer  lip  of 
the  linea  aspera,  and  from  the  external  intermuscular  septum. 
This  muscle  is  covered  over  by  a  powerful  aponeurosis  from 
which  its  fibres  arise.  At  its  orig-in  from  the  linea  aspera, 
and  the  external  intermuscular  septum,  it  is  intimately  blended 
with  the  vastus  internus.  Its  fibres  proceed  in  a  sfeneral 
direction  downward  and  inward  thougfh  the  inferior  fibres 
pass  more  nearly  inward.  It  is  inserted  into  the  outer 
edg-e  of  the  tendon  of  the  rectus  femoris  and  outer  edgfe  of  the 
patella. 

Vastus  Internus. 

The  vastus  internus  arises  from  the  whole  of  the  shaft  of 
the  femur  from  the  anterior  intertrochanteric  line  downward, 
from  the  inner  lip  of  the  linea  aspera,  from  the  internal  inter- 
muscular septum,  from  the  external  intermuscular  septum  and 
from  a  part  of  the  external  lip  of  the  linea  aspera,  where  it 
blends  with  the  vastus  externus.  It  is  inserted  into  the  inner 
edg-e  of  the  tendon  of  the  rectus  femoris  and  inner  edg"e  of  the 
patella. 

The  orig-in  of  the  muscle  is  also  thus  stated:  from  the  inner 
surface  of  the  shaft  of  the  femur,  from  the  anterior  trochanteric 
line  downward,  from  the  front  and  outer  faces,  from  the  internal 
and  external  lips  of  the  linea  aspera  and  the  internal  and 
external  septa. 

It  is  inserted  into  the  inner  edg"e  of  the  tendon  of  the  rectus 
femoris  and  into  the  inner  border  of  the  patella.  The  crureus 
is  here  considered  a  part  of  the  vastus  internus. 

The  insertion  of  the  three  muscles  should  be  thus  stated  : 
They  combine  to  form  a  common  tendon,  the  tendon  of  the 
triceps  extensor  cruris,  which   encloses  the  patella  as  a  sesa- 


266  DESCRIPTIVE  ANATOMY. 

moid  bone  and  is  inserted,  as  the  lig-amentum  patellae,  into  the 
lower  part  of  the  anterior  tubercle  of  the  tibia,  a  bursa  being- 
interposed  between  the  tendon  and  the  upper  part  of  the  tuber- 
cle of  the  tibia. 

The  vasti  muscles  envelop  the  entire  femur  except  the 
middle  lip  of  the  linea  aspera,  and  the  two  extremities  of  the 
bone. 

Action.  This  muscle,  as  its  nam'e  indicates,  is  an  extensor 
of  the  leg-  upon  the  thig-h.  The  central  portion,  or  rectus 
femoris,  is  also  a  flexor  of  the  thig-h  upon  the  pelvis  ;  or,  acting- 
from  below,  of  the  pelvis  upon  the  thigh. 

Internal  Femoral  Region. 

Pectineus  Adductor  Brevis 

Adductor  Ivongus  Adductor  Mag-nus 

The  muscles  of  this  region  are  adductors  of  the  thigh,  that 
is,  they  carry  the  thigh  towards  or  across  its  fellow,  and 
consequently  they  must  all  arise  near  the  middle  line  of  the 
body. 

Pectineus. 

Th.Q  ;pectmeus  is  .a  flat  thin  muscle  which  arises  from  the 
pectineal  line  and  triangle  of  the  pubes  and  the  outer  face  of 
Gmibei'naf  s  ligament.  It  passes  downward  and  is  inserted 
into  the  upper  part  of  the  line  leading  from  the  trochanter 
minor  to  the  linea  aspera. 

It  would  not  be  improper  to  describe  the  remaining  muscles 
of  this  group  as  a  single  muscle  with  a  common  insertion, 
since,  at  the  insertion,  their  fibres  are  so  intimately  blended  as 
to  be  inseparable  without  the  destruction  of  fibres.  They  are 
arranged  in  three  layers,  the  adductor  longus,  which  lies  on 
the  same  plane  as  the  pectineus,  in  front,  next  the  adductor 
brevis  and  last  the  adductor  magnus. 

Abductor  Longus. 

The  adductor  longus  arises  by  a  small,  round  tendon  from 
the  front  of  the  pubes  just  below  the  angle  and  close  to  the 
symphysis.  It  passes  downward  and  outward,  widening  as  it 
descends,  the  tendon  terminating  in  muscular   fibres   which. 


THE  MUSCULAR  SYSTEM.  267 

becoming-  tendinous  in  turn,  are  inserted  into  the  middle  third 
of  the  liuea  aspera,  the  fibres  blending  with  those  of  the  other 
adductors. 

Adductor  Brevis. 

The  adductor  brevis  arises  from  the  body  and  ramus  of  the 
OS  pubis,  just  below  the  spine  and  between  the  gracilis  and 
obturator  externus.  It  passes  downward,  outward  and  back- 
ward, rapidly  becoming  wider  as  it  descends,  and  is  inserted 
into  the  whole  length  of  the  line  leading  from  the  trochanter 
minor  to  the  linea  aspera,  its  insertion  extending  further  down 
than  that  of  the  pectineus,  and  blending  with  the  general 
adductor  tendon. 

Adductor  Magnus. 

The  adductor  ma§)ius  arises  from  the  side  of  the  tuber 
ischii  and  from  the  ischio-pubic  ramus.  It  passes  downward 
and  outward  in  large  distinct  bundles  of  fibres  and  is  inserted 
into  the  whole  length  of  the  linea  aspera  and  by  a  rounded 
tendon  into  the  adductor  tubercle  on  the  internal  cond3^1e 
of  the  femur.  This  muscle  is  pierced  by  five  apertures,  one 
above  the  other,  which  transmit  branches  of  the  femoral  arter3^ 
The  lowest  is  much  the  largest  and  transmits  the  termination 
of  the  femoral  artery  itself,  over  which  the  adductor  longus 
and  magnus  throw  a  tendinous  arch  to  the  vastus  internus, 
forming  what  is  called  Hunter's  canal. 

Action — These  muscles  are  all  adductors,  or  muscles  which 
bring  the  thighs  together  ;  but  in  addition,  as  their  origin  is 
in  front  of  their  point  of  insertion,  the  upper  two  are  flexors. 
When  the  thigh  has  been  rotated  inward,  they  become  power- 
ful outward  rotators.  The  adductors  are  supplied  by  the 
obturator  nerve;  the  pectineus,  usually,  by  the  anterior  crural. 

Scarpa's  Triangle. 

On  the  upper  front  part  of  the  thigh  there  is  an  important 
triangle,  known  as  Scarpa's.  Its  outer  boundary  is  the  sar- 
torius,  its  inner  the  adductor  longus,  its  base  is  Poupart's 
ligament,  its  apex  the  intersection  of  the  sartorius  and  the 
adductor  longus.     Entering  this  triangle  at  the  middle  of  its 


268  DESCRIPTIVE  ANATOMY. 

base  and  passing-  through  it  to  disappear  at  its  apex  are  the 

femoral  artery  and   femoral   vein.     The  floor  of   this  space  is 

formed  by  the  biceps  flexor   femoris,   pectineus  and  adductor 

brevis. 

Muscles  of  the  Leg. 

The  muscles  of  the  leg-  are  divided  into  three  regions,  viz  : 
1st,  anterior  tibial  ;  2d,  posterior  tibial ;  3d,  external  or  fibu- 
lar. 

These  muscles  are  enveloped  by  a  dense  fibrous  membrane 
which  is  found  encircling-  the  leg-  everywhere  except  on  the 
front.  Above  it  is  attached  to  the  head  of  the  tibia  and  fibula 
on  the  sides,  and  is  continuous  with  the  fascia,  lata —  forming- 
with  it  the  popliteal  fascia — behind.  Below,  it  becomes  at- 
tached to  the  bony  prominences  of  the  foot,  forming-  the  ante- 
rior and  two  lateral  aunular  lig-aments.  From  its  deep  face 
it  sends  off  three  broad  inter-muscular  septa,  besides  smaller 
ones  between  individual  muscles.  Two  septa  are  found  on 
the  outer  side,  one  between  the  peroneal  and  anterior  g-roups 
and  one  between  the  peroneal  and  posterior  groups.  The 
third  is  a  broad  transverse  septum  passing-  between  the  super- 
ficial and  deep  muscles  on  the  back  of  the  leg-. 

Posterior  Tibial  Region. 

The  muscles  in  the  posterior  reg-ion  are  placed  in  two  lay- 
ers, superficial  and  deep. 

Superficial  Layer. 

Gastrocnemius  Plantaris  Soleus 

Gastrocnemius. 

The  g-astrocncinius  is  the  larg-e  muscle  which  g-ives  shape 
to  the  calf  of  the  leg.  It  arises  by  two  heads  from  the  upper 
back  part  of  the  condyles  of  the  femur  and  from  the  ridges 
which  connect  the  condyles  with  the  linea  aspera.  The  two 
heads,  as  thev  descend,  converg-e  to  form  the  lower  lateral 
boundaries  of  the  popliteal  space,  and  unite  to  form  the  belly 
of  the  muscle  along  which  a  groove  is  confined  for  some  dis- 
tance.    The  belly  terminates  just  below  the  centre  of  the  leg 


THE  MUSCULAR  SYSTEM.  269 

in  a  large  tendon  called  the  tendo  Achilles,  which  is  inserted 
into  the  lower  back  part  of  the  posterior  tuberosity  of  the  os 
calcis.     It  is  the  larg-est  tendon  in  the  body. 

Action — It  raises  the  heel,  and  continuing"  to  act,  raises  the 
foot. 

Soleus. 

The  soleus  is  a  large  fleshy  muscle  lying-  beneath  the  gas- 
trocnemius. It  has  five  points  of  origin,  viz  :  the  head  and 
upper  half  of  the  posterior  aspect  of  the  fibula,  the  popliteal 
line  and  middle  third  of  the  internal  border  of  the  tibia  and 
from  a  tendinous  arch  stretched  between  its  bony  origins. 
The  muscle  descends  to  terminate  about  the  middle  of  the  leg 
in  the  tendo  Achilles. 

Action — Same  as  the  gastrocnemius. 

Plantaris. 

The  plantaris  is  an  insignificant  muscle  lying  between  the 
gastrocnemius  and  soleus.  It  arises  from  the  back  part  of 
the  external  condyle  of  the  femur  in  common  with  the  external 
head  of  the  gastrocnemius,  the  belly  of  the  muscle  passing 
downward  and  inward  between  the  gastrocnemius  and  soleus 
to  terminate  in  a  tendon  which,  escaping  to  the  inner  side  of 
the  two  muscles,  passes  down  either  to  be  inserted  into  the 
posterior  tuberosity  of  the  os  calcis  or  to  be  lost  in  the  side  of 
the  tendo  Achilles. 

Action — Same  as  gastrocnemius. 

The  three  muscles  just  described  form  the  triceps  surae. 
They  are  supplied  by  the  internal  popliteal  nerve. 

Deep  Layer. 

Popliteus  Flexor  Longus  Digitorum 

Tibialis  Posticus  Flexor  Longus  Pollicis 

Popliteus. 

The  -popliteus  is  a  small  triangular  muscle  resembling  the 
anconeus  in  the  upper  extremity.  It  arises  by  its  tendinous 
apex  from  a  groove  on  the  external  condyle  of  the  femur  and 
passes  downward  and  inward,  adhering  to  the  head  of  the 
fibula,  the  posterior  ligament  of  the  knee-joint  and  the  under 


270  DESCRIPTIVE  ANATONY. 

surface  of  the  fascia  which  covers  it,  is  inserted  into  the  tibi  a 
above  and  as  low  down  as  the  oblique  or  popliteal  line  on  its 
posterior  face. 

Action — It  flexes  and  inverts  the  leg".  It  is  supplied  by  the 
internal  popliteal  nerve. 

Flexor  Longus  Pollicis. 

Th.Q.  flexor  long-iis  pollicis  arises  from  the  lower  two-thirds 
of  the  fibula,  except  the  last  inch,  and  from  the  intermuscular 
septum.  It  descends  behind  the  internal  malleolus  into  the 
sole  of  the  foot,  crosses  the  tendon  of  the  flexor  long-us  dig-i- 
torum  and  is  inserted  into  the  base  of  the  last  phalanx  of  the 
great  toe. 

Action — It  flexes  the  last  phalanx  of  the  great  toe. 

Flexor  Longus  Digitorum. 

The  flexor  long'us  dig-itoruin  arises  from  the  lower  two- 
thirds  of  the  tibia,  except  the  last  two  or  three  inches,  and 
from  the  intermuscular  septum.  It  passes  downward  behind 
the  internal  malleolus,  divides  into  four  tendons,  which  are 
crossed  by  the  flexor  longus  pollicis,  and  are  inserted  into  the 
last  phalanges  of  the  four  outer  toes. 

Its  action  is  indicated  by  its  name,  after  flexing  the  toes  it 
extends  the  foot  on  the  leg. 

Tibialis  Posticus. 

The  tibialis  posticus  arises  from  the  whole  leng-th  of  the 
posterior  surface  of  the  interosseous  membrane,  from  the  ad- 
jacent edges  of  the  tibia  and  fibula  and  from  the  intermuscular 
septum.  It  descends  behind  the  internal  malleolus  and  is  in- 
serted into  the  tuberosity  of  the  scaphoid  bone  and  into  the 
internal  cuneiform  bone. 

Action — It  is  an  extensor  and  abductor  of  the  foot. 

The  three  last  muscles  all  arise  from  the  interosseous  mem- 
brane; and  as  the  flexor  longus  pollicis  arises  from  the  outer 
bone  of  the  leg  and  is  inserted  into  the  inner  toe,  it  must  cross 
the  flexor  longus  digitorum.  This  crossing  takes  place  in  the 
sole  of  the  foot  and  is  known  as  the  decussation  of  the  tendons, 
which  are  connected  at  this  point  by  a  small  slip. 


THE  MUSCULAR  SYSTEM.  271 

The  Interosseous  Membrane. 

The  iuterosseous  membrane  is  a  strong- ligamentous  membrane 
which  passes  from  tibia  to  fibula  and  is  attached  to  their  ad- 
jacent edo-es,  after  the  manner  of  the  interosseous  membrane 
of  the  forearm.  On  its  posterior  aspect  it  is  entirely  appro- 
priated by  the  tibial  muscles.  The  muscles  in  the  deep  layer 
are  separated  from  those  in  the  superficial  layer  by  a  strong" 
thick  fascia. 

Anterior  Region  of  the  Leg. 

.Tibialis  Anticus  Kxtensor  Longus  Dig-itorum 

Kxtensor  Proprius  Pollicis 

Of  the  three  muscles  in  this  group  two  have  four  points  of 
origin  in  common.  These  four  points  are  as  follows:  1st, 
outer  tuberosity  of  the  tibia  ;  2d,  investing  fascia  of  the  leg  ; 
3d,  intermuscular  septum  ;  4th;  interosseous  membrane. 

Tibialis  Anticus. 

The  tibialis  anticus  arises  from  the  common  origin  (the 
outer  tuberosity  of  the  tibia,  the  investing  fascia,  the  inter- 
muscular septum  between  itself  and  the  extensor  longus  digi- 
torum,  and  the  interosseous  membrane)  and  from  the  upper  two- 
thirds  of  the  outer  face  of  the  tibia.  It  passes  downward  to 
terminate  in  a  tendon  which  runs  beneath  the  anterior  annular 
ligament  and  is  inserted  into  the  inner  and  under  surface  of 
the  internal  cnneiform  bone  and  into  the  base  of  the  metatar- 
sal bone  of  the  great  toe. 

Action — It  flexes  the  foot;  and,  according  as  it  acts  with  the 
tibialis  posticus  or  the  peronei,  it  inverts  or  everts  the  foot. 

Extensor  Longus  Digitorum. 

The  extensor  loui^us  di^^itoriini  arises  from  the  common  ori- 
gin— outer  tuberosity,  investing  fascia,  intermuscular  septum 
between  itself  and  the  tibialis  anticus  internally  and  the  pero- 
neus  longus  externally,  and  the  interosseous  membrane  and 
from  the  head  and  whole  length  of  the  anterior  aspect  of  the 
shaft  of  the  fibula.  It  descends  and  divides  into  five  tendons, 
which  pass  beneath  the  anterior  annular  ligament  and  are  in- 


272  DESCRIPTIVE  ANATOMY. 

serted  as  follows:  one  Into  the  base  of  the  metatarsal  bone  of 
the  little  toe,  the  other  four  into  the  backs  of  the  four  lesser 
toes  after  the  manner  of  extensor  tendons.  That  part  of  the 
muscle  inserted  into  the  base  of  the  metatarsal  bone  of  the  little 
toe,  and  arising  from  the  lower  fourth  of  the  fibula,  is  some- 
times called  the  peroneus  tertius. 

Action — It  extends  the  toes;  and,  by  its  insertion  into  the 
metatarsal  bone  of  the  little  toe,  flexes  the  foot. 

Extensor  Proprius  Pollicis. 

The  extensor  proprius  ■pollicis  is  shorter  than  the  two  pre- 
ceding muscles  and  lies  between  and  is  overlapped  by  them. 
It  arises  from  the  middle  two-fourths  of  the  shaft  of  the  fibula 
and  from  the  interosseous  membrane,  and  terminates  in  a  tendon 
which  passes  beneath  the  anterior  annular  ligament  and  is  in- 
serted into  the  base  of  the  last  phalanx  of  the  great  toe.  Its 
action  is  indicated  by  its  name. 

The  anterior  annular  ligament  is  a  strong  oblique  ligament- 
ous band  which  binds  the  tendons  of  the  three  preceding  mus- 
cles down  on  the  front  of  the  ankle.  It  consists  of  an  upper 
part  passing  from  the  tibia  to  the  fibula  and  containing  the 
compartment  for  the  tibialis  anticus;  and  a  lower  portion,  at- 
tached above  to  the  inner  malleolus  and  below  to  the  lesser 
process  of  the  os  calcis  which  forms  the  swing  ligament  con- 
taining the  sheath  for  the  extensor  longus  digitorum  and  the 
extensor  proprius  pollicis.  A  small  offshoot  of  this  band  passes, 
to  the  plantar  fascia. 

These  muscles  are  supplied  by  the  anterior  tibial  nerve. 

External  Region  of  the  Leg. 

Peroneus  Longus  Peroneus  Brevis 

Peroneus  Longus 

'^\\.^  -peroneus,  or  fihularis,  longus  arises  from  the  head  and 
upper  two-thirds  of  the  outer  aspect  of  the  shaft  of  the  fibula, 
from  the  investing  fascia  and  the  intermuscular  septa  between 
itself  and  the  extensor  longus  digitorum  on  the  inner  and  the 
posterior  group  on  the  outer  side — Below  another  septum  is 
found  between    the  two    peroneal   muscles.     It   descends  to> 


THE  MUSCULAR  SYSTEM.  273 

terminates  in  a  tendon  which  passes  behind  the  external  mal- 
leolus, through  the  louver  groove  on  the  outer  surface  of  the 
OS  calcis,  reaches  the  sole  of  the  foot  and  is  directed  across  it 
obliquely  forward  and  inward,  through  a  groove  in  the  cuboid 
bone,  to  be  inserted  into  the  base  of  the  metatarsal  bone  of  the 
great  toe. 

Action — It  is  an  extensor  of  the  foot. 

Peroneus  Brevis. 

The  fieroiieiis,  or  Jibularis,  brevis  derives  its  name  from  its 
position  and  because  its  origin  and  insertion  are  both  short  of 
the  preceding  muscle,  beneath  which  it  lies.  It  arises  from 
the  lower  two-thirds  of  the  outer  aspect  of  the  shaft  of  the  fib- 
ula and  from  the  intermuscular  septum,  descends  behind  the 
external  malleolus,  throug-h  the  upper  groove  on  the  outer  sur- 
face of  the  OS  calcis,  and  is  inserted  into  the  base  of  the  meta- 
tarsal bone  of  the  little  toe. 

Action — It  extends  the  foot. 

The  two  peronei  muscles,  as  they  are  passing  the  outer 
malleolus,  are  held  down  by    the  external    annular  ligament 

They  are  supplied  by  the  musculo-cutaneous  nerve. 
Muscles  of  the  Foot. 

The  foot  is  divided  into  two  regions,  dorsal  and  plantar. 

The  fascia  covering  the  dorsum  of  the  foot  is  thin  and 
membranous.  Above  it  is  continuous  with  the  anterior  annu- 
lar ligament,  while  on  the  sides  it  becomes  attached  to  the 
plantar  fascia.  On  either  side  there  is  a  strong  lateral  annular 
ligament  each  continuous  above  with  the  fascia  of  the  leg  and 
below  with  the  plantar  fascia.  The  iutcDial  cDinular  ligament 
is  attached  to  the  internal  malleolus  above  and  to  the  inner  face 
of  the  OS  calcis  below.  It  forms  grooves  for  the  passage  of 
the  flexor  tendons. 

The  external  amuilar  ligament  is  attached  to  the  internal 
malleolus  and  to  the  outer  margin  of  the  os  calcis  forming 
grooves  for  the  peroneal  tendons. 

Dorsum  of  the  Foot. 
Extensor  Brevis  Digitorum. 

The  extensor  brevis  digitorum  arises   from  the   upper  and 

Des  Anat— 18 


274  DESCRIPTIVE  ANATOMY. 

outer  aspect  of  the  os  calsis  and  passing  forward  and  inward 
divides  into  four  tendons  the  innermost  of  which  is  inserted  into 
the  base  of  the  first  phalanx  of  the  great  toe,  the  other  three 
into  the  backs  of  the  next  three  toes  in  common  with  the  long 
extensor  tendons. 

Its  name  indicates  its  action. 

The  Sole  of  the  Foot. 
The  Plantar  Fascia. 

When  the  thick  skin  on  the  sole  of  the  foot  has  been  removed, 
there  is  brought  into  view  a  thick  mass  of  fatty  tissue  and 
beneath  this  a  strong  fascia  called  iho.  plantar  fascia.  It  con- 
sists of  a  strong,  thick  central  portion  and,  on  either  side, 
continuous  with  this,  a  thinner  lateral  portion.  The  central 
portion  begins  behind  at  the  under  surface  of  the  os  calcis, 
runs  forward  and  just  beyond  the  middle  of  the  sole  divides 
into  five  branches  each  of  which  passes  forward  to  the  base 
of  a  corresponding  toe.  The  muscles  of  the  sole  all  lie  beneath 
(or,  in  the  erect  position,  above)  this  fascia  and  are  divided  into 
groups  in  accordance  with  the  subdivisions  of  the  plantar 
fascia,  viz  :  a  central  and  two  lateral  groups.  The  propriety 
of  this  division  is  shown  by  the  fact  that  the  plantar  fascia 
sends  up  to  the  bone  intermuscular  or  dividing  septa  from 
the  line  of  union  of  the  central  aud  two  lateral  portions. 

In  describing  these  muscles,  however,  they  are  taken  in 
layers,  of  which  there  are  three.  When  the  plantar  fascia, 
the  dissection  of  which  is  the  first  step,  has  been  removed, 
the  first  layer,  consisting  of  one  muscle  in  each  group,  is  ex 
posed.  This  constitutes  the  second  view  in  the  dissection  of 
the  sole. 

First  Layer. 

Abductor  Pollicis  Abductor  Minimi  Digiti 

Flexor  Brevis  Digitorum. 

The  three  muscles  forming  the  first  layer  have  a  common 
origin,  viz;  1st,  the  under  surface  of  the  os  calcis;  2d,  the 
plantar  fascia  which  covers  them;  3d,  the  intermuscular  septa 
'which  separate  them.     Some  of  the  plantar   fascia  should  be 


THE  MUSCULAR  SYSTEM.  275 

left  on  the  muscles  in   dissecting-   them,  since  it  is  a  part  of 
their  orig-in. 

Abductor  Pollicis. 

The  abductor  pollicis  is  the  innermost  of  the  three  muscles 
of  the  first  layers.  It  arises  from  the  common  orig-in  and  is 
inserted  into  the  inner  side  of  the  base  of  the  first  phalanx  of 
the  g-reat  toe. 

Its  name  indicates  its  action. 

Abductor  Minimi  Digiti. 

The  abductor  minimi  dig-iti  is  the  outer  of  the  three  muscles 
in  the  first  laj^er.  It  arises  from  the  common  orig-in  and  is 
inserted  into  the  outer  side  of  the  base  of  the  first  phalanx  of 
the  little  toe. 

Its  name  indicates  its  action. 

Flexor  Brevis  Digitorum. 

Th^  flexor  brevis  dig-itoruin  lies  in  the  centre  of  the  first 
layer.  It  arises  from  the  common  orig-in,  passes  forward  and 
divides  into  four  tendons  for  the  four  lesses  toes.  Each  ten- 
don splits  to  allow  the  passag-e  of  the  tendon  of  the  long-  flexor 
and  is  inserted  into  the  sides  of  the  shaft  of  the  second  pha- 
lanx. 

Its  name  indicates  its  action. 

Second  Layer. 

Musculus  Accessorius  Lumbricales 

The  second  layer,  exposed  by  removing-  the  first,  is  the 
third  view  in  the  dissection  of  the  sole.  It  consists  of  the 
musculus  accessorius,  the  lumbricales  and  the  tendons  of  the 
flexor  longus  pollicis  and  flexor  longus  digitorum.  These  two 
tendons,  soon  after  entering-  the  sole  from  behind  the  internal 
malleolus,  cross  each  other  forming-  their  decussation  and  are 
also  connected  by  slips  so  that  one  muscle  cannot  act  independ- 
ently of  the  other,  but  throws  the  part  to  which  it  is  attached 
into  slig-ht  motion. 

Musculus  Accessorius. 

The  musculus  accessorius  arises  tendinous  and  fleshy  from 
the  under  surface  of  the  os  calcis  and  passing-  forward  is  in- 


276  DESCRIPTIVE  ANATOMY. 

serted  into  the  outer  side  and  upper  surface  of  the  tendon  of 
the  flexor  longfus  dig-itorum  just  as  it  splits  into  its  four 
branches. 

Action — It  corrrects  the  obliquity  which  would  otherwise 
be  imparted  to  the  four  lesser  toes  by  the  action  of  the  long- 
flexor. 

Lumbricales. 

The  lumbricales  are  four  little  worm-like  muscles,  three  of 
which  arise  from  the  bifurcation  of  the  tendon  of  the  flexor 
long-us  dig-itorum,  while  the  fourth  spring-s  from  the  inner 
side  of  the  inner  tendon  of  that  muscle.  They  pass  between 
the  toes  and  are  inserted  into  the  tibial  side  of  the  extensor 
tendons  of  the  four  lesser  toes. 

Action — -They  aid  the  flexor  long-us  dig-itorum. 

Third  Layer. 

Flexor  Brevis  Pollicis         Flexor  Brevis  Minimi  Digiti 
Adductor  Pollicis  Tranversus  Pedis 

This  layer,  constituting-  the  fourth  view  in  the  dissection 
of  the  sole  of  the  foot,  is  exposed  by  removing-  the  second 
layer. 

Flexor  Brevis  Pollicis. 

'X:\iQ  fiexor  brevis  -pollicis  arises  from  the  cuboid  bone,  the 
external  cuneiform  bone  and  the  expanded  tendon  of  the  tibi- 
alis posticus.  It  is  inserted  into  both  sides  of  the  base  of  the 
first  phalanx  of  the  g-reat  toe,  each  tendon  having-  a  sesamoid 
bone  in  it. 

Adductor  Pollicis. 

The  adductor  pollicis  arises  from  the  cuboid  bone,  from  the 
sheath  of  the  tendon  of  the  peroneus  long-us  and  from  the 
bases  of  the  adjoining-  metatarsal  bones  (second,  third  and 
fourth).  It  is  inserted  into  the  outer  side  of  the  base  of  the 
first  phalanx  of  the  great  toe. 

Flexor  Brevis  Minimi  Digiti. 

'X:\iQ  flexor  brevis  minimi  dig-iti  arises  from  the  base  of  the 
fifth  metatarsal  bone  and  is  inserted  into  the  outer  side  of  the 
first  phalanx  of  the  little  toe. 


THE  MUSCULAR  SYSTEM.  277 


Transversus  Pedis. 

The  ti'ansversus  pedis  arises  by  slips  from  the  heads  of  the 
four  outer  metatarsal  bones,  and  passing-  inward  is  inserted 
into  the  outer  side  of  the  base  of  the  first  phalanx  of  the  gfreat 
toe. 

Action — It  is  an  adductor  of  the  gfreat  toe. 

Interosseous  Muscles. 

Lying"  between  the  metacarpal  bones  of  the  hand  and  the 
metatarsal  bones  of  the  foot  are  certain  small  muscles  called 
from  their  position  interosseous.  In  each  member  there  are 
seven  of  these  muscles,  four  dorsal  and  three  plantar.  They 
are  bipenniform  muscles,  arising-  from  the  metacarpal  or  met- 
atarsal bone  and  inserted  into  the  first  phalanx.  The  first 
dorsal  interosseous  of  the  hand  is  much  larg-er  than  the  others 
and  is  called  the  abductor  indicis. 

The  Muscles  of  the  Face. 

The  muscles  of  the  face  are  arrang-ed  in  g-roups,  viz:  those 
connected  with  the  orbit,  with  the  nose,  the  mouth  and,  a  very 
unimportant,  g-roup  connected  with  the  auricle. 

Orbital  Group — Three  Muscles. 
Orbicularis  Palpebrarum. 

The  orhicularis-fxilpebrariiin  is  an  elliptical  muscle,  lying- 
just  beneath  the  skin,  in  front  of  the  orbit,  the  portion  which 
lies  on  the  lid  being-  thinner  and  paler  than  the  rest.  It  arises 
from  the  tendo  oculi  and  adjacent  bone;  and  the  fibres,  form- 
ing- an  ellipse  around  the  orbit,  return  to  the  place  from  which 
they  started.  The  tendo  oculi  is  a  fibrous  cord,  which  is  at- 
tached by  one  end  to  the  orbital  aspect  of  the  nasal  process  of 
the  superior  maxilla,  while  the  other  end  bifurcates  to  be  at- 
tached to  the  inner  extremities  of  the  tarsal  cartilag-es. 

Kxternally  the  orbicularis  palpebrarum  is  attached  to  the 
temporal  fascia. 

Action — It  closes  the  eyelids.  -  It  is  one  of  the  sphincter 
muscles,  but  in  its  action  differs  from  most  of  them  in  being" 


278  DESCRIPTIVE  ANATONY. 

immovably  attached  at  its  extremities.  When  its  fibres  con- 
tract they  bring"  the  eyelids  togfetheJ  in  a  line  corresponding- 
to  its  points  of  attachment,  whereas  most  sphincter  muscles 
close  the  aperture  which  they  surround  by  an  approximation 
of  all  their  fibres  at  the  same  time,  and  in  the  same  proportion, 
towards  the  centre  of  the  aperture,  e.  §-.,  the  orbicularis  oris, 
in  the  act  of  whistling-,  since  it  has  no  bony  attachment. 

Corrugator  Supercilii. 

The  corriigator  supercilii  is  a  small  muscle,  which  arises 
from  the  inner  extremity  of  the  supercilliary  ridg-e,  on  each 
side,  passes  outward  and  is  lost  in  the  deep  face  of  the  orbicu- 
laris palpebrarum. 

Action — It  throws  the  skin  of  the  forehead  into  vertical  folds, 
i.  e.,  corrug-ates  the  brow. 

Tensor  Tarsi. 

The  tensor  tarsi,  or  Horner  s  muscle,  is  very  small.  It 
arises  from  the  orbital  surface  of  the  lachrymal  bone,  passes 
outward  and  divides  into 

Cranial  Group — One  Muscle. 

Occipito-Frontalis. 

The  occi^ito-frontalis  of  either  side,  arises  from  the  superior 
curved  line  of  the  occipital  bone  and  the  mastoid  process.  It 
is  tendinous  at  its  origin  but  becomes  fleshy  as  it  passes  forward; 
and  then,  as  it  is  mounting-  over  the  vault  of  the  cranium,  it 
forms  a  broad,  aponeurosis  and  descending-  on  the  forehead 
ag-ain  becomes  fleshy  to  be  lost  in  the  orbicularis  palpebrarum 
and  corrugator  supercilii,  its  innermost  fibres  forming-  the 
pyramidalis  nasi  muscle. 

Action — It  raises  the  brows  and  throws  the  skin  of  the  fore- 
head into  wrinkles. 

Nasal  Group — Three  Muscles. 

Pyramidalis  Nasi. 

The  pyramidalis  nasi  is  formed  by  the  innermost  fibres  of 
the  occipito-frontalis,  which  descending-,  are  lost  on  the  bridge 
of  the  nose. 


THE  MUSCULAR  SYSTEM.  279 

Action — It  draws  down  the  inner  extremity  of  the  eyebrow 
and  elevates  the  nose. 

Compressor  Naris. 

The  comf)ressor  naris,  triang-ular  in  shape,  arises  from  the 
canine  fossa  on  the  superior  maxilla  by  its  apex  and,  mounting- 
on  the  side  of  the  nose,  meets  its  fellow  of  the  opposite  side 
in  a  tendinous  raphe  on  the  bridge  of  the  nose. 

Action — The  two  are  supposed  to  compress  the  nostrils. 

Depressor  Alae  Nasi. 

The  depressor  alee  nasi  is  found  Just  beneath  the  mucous 
membrane  of  the  upper  lip.  It  arises  from  the  incisive  fossa 
of  the  superior  maxilla  and  is  inserted  into  the  ala  of  the  nose. 
Its  name  indicates  its  action. 

The  muscles  of  the  face  are  nearly  all  small  and  pale  and 
fatty.  As  a  rule  they  arise  from  bone  and  are  inserted  into 
soft  parts.  Their  action  produces  the  varying-  expression  of 
which  the  face  is  capable. 

Muscles  of  the  Mouth. 

The  muscles  of  the  mouth  consist  of  two  g-roups,  superior 
and  inferior  labial  groups  and  one  muscle,  the  orbicularis  oris, 
which  belong-s  to  both  g-roups. 

Orbicularis  Oris. 

The  orbicularis  oris  is  the  sphincter  muscle  of  the  mouth  ; 
as  it  has  but  slig-ht  connection  with  bone,  this  attachment  may 
be  disreg-arded.  It  consists  of  two  seg-ments,  one  in  each  lip, 
which  meet  at  the  ang-les  of  the  mouth. 

Action — It  can  close  the  mouth  in  two  ways,  either  by  bring- 
ing- the  lips  tog-ether  in  a  horizontal  line  or  by  approximating- 
the  ang-les  of  the  mouth  at  the  same  time. 

Superior  Labial  Group — Five  Muscles. 

Levator  Labii  Susperioris  Alaeque  Nasi. 

The  levator  lahii  susperioris  alceque  nasi  arises  from  the 
nasal  process  of  the  superior  maxilla  and  descending-  divides 
into  two  slips,  one  of  w^hich  is  inserted  into  the  ala  of  the  nose 


280  DESCRIPTIVE  ANATOMY. 

while  the  other  continues  on  to  be  inserted  in   the  upper   lip. 
Its  name  indicates  its  action. 

Levator  Labii  Superioris  Propius. 

This  muscle  arises  from  the  orbital  ridge  of  the  superior 
maxilla  and  descends  to  be  inserted  into  the  upper  lip.  Its 
name  indicates  its  action. 

Levator  Anguli  Oris. 

The  levator  ang'uli  oris,  or  canine  muscle,  arises  from  the 
canine  fossa  of  the  superior  maxilla  and  passes  downward  and 
outward  to  be  inserted  into  the  ang-le  of  the  mouth.  Its  name 
indicates  its  action. 

The  Zygomatic  Muscles — Two. 

The  zygomatic  are  two  small  muscles  which  arise  from  the 
Z3'g"omatic  process  of  the  malar  bone  and  pass  downward  and 
inward.  The  zygomaticus  major,  the  lower  one,  is  inserted 
into  the  ang-le  of  the  mouth  and  the  zygoniaticus  minor  into 
the  upper  lip. 

Action — They  carry  the  angle  of  the  mouth  upward  and 
outward. 

Inferior  Labial  Group — Three  Muscles. 

Q,uadratus  Menti. 

The  quadratus  menti,  or  depressor  labii  inferioris,  is  a 
square-shaped  thin  muscle  which  arises  from  the  oblique  line 
on  the  front  of  the  lower  jaw  near  the  symphysis  and,  passing 
upward,  is  lost  in  the  lower  lip.  Its  synonym  indicates  its 
action. 

Triangularis. 

The  triang-alaris  or  depressor  ang-iili  oris,  arises  by  its 
base  just  external  to  the  preceding  and  is  inserted  by  its  apex 
into  the  angle  of  the  mouth.     Its  synonym  indicates  its  action. 

Levator  Labii  Inferioris. 

The  levator  labii  inferioris  lies  just  beneath  the  mucous 
membrane.  It  arises  from  the  incisive  fossa  of  the  inferior 
maxilla  and  is  inserted  into  the  integument  of  the  chin.  Its 
action  is  indicated  by  its  name. 


THE  MUSCULAR  SYSTEM.  281 

The  Ocular  Group. 

Levator  Palpebrae  Superioris 
Superior  Rectus  Inferior  Rectus 

External  Rectus  Internal  Rectus 

Superior  Oblique  Inferior  Oblique 

The  muscles  forming  this  group  are  found  within  the  orbit. 
All  of  them,  except  the  levator  palpebral  superioris,  are 
attached  to  the  eye-ball,  and  all,  except  the  two  oblique  mus- 
cles, arise  at  the  apex  of  the  orbit  and  pass  forward  flat, 
straight  and  widening  as  the}"  advance  toward  their  insertion. 
Four  of  them,  from  the  direction  of  their  fibres,  are  called 
recti  and  are  concerned  in  moving  the  eye-ball.  They  are 
distinguished  as  :  1st,  superior  rectus,  because  it  lies  above 
the  eye-ball  and  draws  the  front  of  the  eye  upward  ;  2d,  infe- 
rior rectus,  because  it  lies  below  the  eye-ball  and  draws  its 
front  downward  ;  3d,  external  rectus,  because  it  lies  external 
to  the  e3"e-ball  and  draws  its  front  outward  ;  4th,  internal  rec- 
tus, because  it  lies  internal  to  the  eye-ball  and  draws  its  front 
inward.  By  a  combined  action  of  these  muscles  the  front  of 
the  eye  can  be  moved  in  all  directions  intermediate  between 
those  mentioned.  All  the  recti  arise  from  the  apex  of  the  orbit, 
that  is  the  margin  of  the  optic  foramen,  and  also  receive  an 
origin  from  the  fibrous  sheath  of  the  optic  nerve.  They  run 
forward  and  are  inserted  into  the  sclerotic  coat  about  one-fourth 
of  an  inch  behind  the  circumference  of  the  cornea.  Some  give 
as  the  origin  of  three  of  these  muscles  the  ligament  of  Zinn, 
which  is  a  fibrous  band  attached  around  the  lower  portion  of 
the  circumference  of  the  optic  foramen.  This,  however,  is  an 
unnecessary  refinement.  These  muscles  difiFer  but  slightly  in 
size  and  length. 

Levator  Palpebrae  Superioris. 
Lying  just  beneath  the  orbit,  and  between  it  and  the  superior 
rectus,  is  a  muscle  closely  resembling  the  recti  called  levator 
f)alpchr(c  superioris  since  its  action  is  to  raise  the  upper  lid. 
It  arises  from  the  upper  margin  of  the  optic  foramen  and 
sheath  of  the  optic  nerve,  passes  forward  and  is  inserted  into 
the  upper  edge  of  the  superic^r  tarsal  cartilage. 


282  DESCRIPTIVE  ANATOMY. 


Inferior  Rectus. 

The  inferior  rectus  arises  from  the  lower  margfin  of  the  optic 
foramen  and  from  the  sheath  of  the  optic  nerve.  It  passes 
forward  and  is  inserted  into  the  under  surface  of  the  sclerotic 
about  one-fourth  of  an  inch  behind  the  cornea. 

External  Rectus. 

The  external  rectus  arises  by  a  forked  origin  from  the  outer 
margin  of  the  optic  foramen  and  from  the  sheath  of  the  optic 
nerve.  It  passes  forward  and  is  inserted  into  the  outer  sur- 
face of  the  sclerotic  coat  about  one-fourth  of  an  inch  behind 
the  circumference  of  the  cornea.  It  is  important  to  remember 
its  forked  origin,  since  many  nerves  pass  through  the  interval 
between  its  head. 

Internal  Rectus. 

The  internal  rectus  arises  from  the  inner  margin  of  the  optic 
foramen  and  sheath  of  the  optic  nerve.  It  passes  forward  and 
is  inserted  into  the  inner  surface  of  the  sclerotic  coat  about  one- 
fourth  of  an  inch  behind  the  circumference  of  the  cornea. 

Superior  Rectus. 

The  superior  rectus  arises  from  the  upper  margin  of  the 
optic  foramen  and  from  the  fibrous  sheath  of  the  optic  nerve. 
It  passes  forward  and  is  inserted  in  the  sclerotic  coat  one- 
fourth  of  an  inch  behind  the  cornea.  It  is  the  thinnest  of  the 
recti. 

Inferior  Oblique. 

The  inferior  oblique  is  a  narrow  and  thin  muscle,  arising 
from  the  orbital  surface  of  the  supsrior  maxilla,  near  the  inner 
side  of  the  orbit.  It  passes  out  beneath  the  eye-ball  and 
inferior  rectus  to  be  inserted  into  the  sclerotic  near  the  entrance 
of  the  optic  nerve,  on  the  outer  under  aspect  of  the  eye-ball. 

Superior  Oblique  or  Trochlearis. 

The  superior  oblique  arises  from  the  inner  margin  of  the 
optic  foramen  and  sheath  of  the  optic  nerve.  It  passes  forward 
along  the    upper  inner  wall  of  the  orbit  to  its  front,     where, 


THE  MUSCULAR  SYSTEM.  283 

becoming-  tendinous,  it  plays  throug-h  a  cartilaginous  ring-  fixed 
to  the  fovea  trochlearis  :  thence  its  tendon  passes  outward  and 
backward,  beneath  the  superior  rectus,  to  be  inserted  into  the 
outer  aspect  of  the  sclerotic  about  half  way  between  the 
circumference  of  the  cornea  and  the  entrance  of  the  optic  nerve. 
Action — Its  action  is  computed  from  the  pully  at  the  fovea 
trochlearis — hence  it  rotates  the  eye-ball  on  itsantero-posterior 
axis  and  draws  it  forward. 

Muscles  of  Mastication. 

Masseter  Buccinator 

Temporal  External  Pteryg-oid 

Internal   Pteryg-oid 

Masseter. 

The  masseter  arises  from  the  zygfomatic  process  of  the 
superior  maxilla  and  from  the  anterior  two  thirds  of  the 
zygomatic  arch  by  a  bundle  of  fibres  which  pass  downward 
and  backward  to  be  inserted  into  the  ang-le  and  posterior  part 
of  the  outer  surface  of  the  lower  jaw.  Beneath  these  fibres 
is  a  smaller  bundle  arising-  from  the  posterior  third  of  the 
zygomatic  arch  and  passing-  downward  and  forward  to  be  in- 
serted into  the  outer  face  of  the  ramus  nearly  to  the  basilar 
border  of  the  bone. 

Action — The  two  muscles,  acting-  tog-ether,  draw  the  lower 
jaw  powerfully  upward  and  press  the  teeth  firmly  ag-ainst  the 
teeth  of  the  upper.  The  superficial  fibres  draw  the  jaw 
forward  while  the  deep  carry  it  backward. 

The  masseter  is  covered  by  a  strong-  fascia,  derived  from 
the  cervical  fascia,  which  is  attached  below  to  the  lower  jaw, 
and  blends  with  the  deep  cervical  fascia,  while  above  it  is 
attached  to  the  zyg-oma  and  forms  the  parotid  fascia. 

Buccinator. 

The  buccinator^  or  trumpeter's  muscle,  is  the  bulkiest 
element  of  the  cheek.  It  arises  from  the  alveolar  process  of 
the  superior  maxilla,  from  the  external  oblique  ridg-e  of  the 
lower  jaw,  as   far  forward   as  the  second    bicuspid  tooth  and 


284  DESCRIPTIVE  ANATOMY. 

from  the  pterygo-maxillary  lig-ament.  Its  fibres  converge  to 
be  inserted  into  the  ang-le  of  the  mouth. 

Action^The  buccinators  compress  the  cheeks,  keeping"  food 
between  the  teeth  or  expelling  air  through  the  lips. 

The  -pteryg-o-niaxillary  lig-a7nent  extends  from  the  hamular 
process  of  the  pterygoid  plate  to  the  posterior  extremity  of 
the  molar  ridge  of  the  lower  jaw.  In  front  it  gives  origin  to 
some  of  the  fibres  of  the  buccinator  and  behind  to  the  superior 
constrictor  of  the  pharynx. 

Temporal. 

This  muscle  is  found  in  a  fossa,  and  is  covered  by  a  fascia, 
bearing  the  same  name.  The  temporal  fascia  is  a  dense, 
shining  aponerosis  which  is  attached  above  to  the  temporal 
ridge  on  the  side  of  the  skull ;  while  below  it  divides  into  two 
layers,  one  seizing  the  outer  and  One  the  inner  edge  of  the 
upper  border  of  the  zygomatic  arch.  The  deep  surface  of  the 
fascia  gives  origin  to  part  of  the  temporal  muscle. 

The  temporal  is  a  radiated  muscle  occupying  the  temporal 
fossa.  It  arises  from  the  whole  of  the  temporal  fossa,  from 
the  whole  length  of  the  temporal  ridge  and  from  the  temporal 
fascia  which  covers  it.  It  passes  downward,  its  fibres  con- 
verging, and  is  inserted  into  the  apex  and  inner  side  of  the 
coronoid  process  of  the  inferior  maxilla. 

Action — It  is  a  powerful  elevator  of  the  lower  jaw,  acting 
in  concert  with  the  masseter.  Its  power  is  greatest  when 
the  jaw  is  depressed,  while  the  power  of  the  masseter  increases 
as  the  jaws  are  approximated. 

External  Pterygoid. 

The  external  pteiyjo-oid  arises  from  the  lower  surface  of  the 
greater  wing  of  the  sphenoid,  from  the  pterygoid  ridge  and 
sphenoidal  spine  and  from  the  whole  of  the  outer  face  of  the 
external  pterygoid  plate.  The  fibres  pass  backward  and  out- 
ward and  narrow  to  a  tendon  which  is  inserted  into  the  neck 
of  the  condyle  of  the  lower  jaw  and  into  the  inter-articular 
fibro-cartilage. 

Action — The  two  muscles  acting  together,  will  carry  the 
lower  jaw  directly  forward.     One  muscle  alone  draws  the  jaw 


THE  MUSCULAR  SYSTEM.  285 

forward  and  to  the  opposite  side.  It  is  the  alternate  action 
of  the  two  muscles  which  produces  the  g-rinding-  motion  nec- 
essary for  bruising*  the  food. 

Internal  Pterygoid. 

The  internal  pterygoid,  or  internal  mas  seter  3X\^q^  from  the 
inner  face  of  the  outer  pterygoid  plate,  from  the  g*rooved 
posterior  face  of  the  tuberosity  of  the  palate  and  occasionally 
by  a  slip  from  the  tuberosity  of  the  superior  maxilla.  It 
passes  downward,  outward  and  is  inserted  into  the  inner  face 
of  the  angle  and  ramus  of  the  lower  jaw. 

Action^ — It  acts  almost  exactly  like  the  superficial  fibres 
of  the  masseter,  drawing*  the  jaw  forward  and  upward.  Its 
origin  being*  nearer  the  middle  line,  however,  it  also  draws 
the  jaw  inward,  thus  aiding*  the  external  pteryg*oid  in  grind- 
ing* the  food. 

All  the  muscles  of  mastication  are  supplied  by  the  muscular 
branches  of  the  inferior  maxillary  division  of  the  fifth,  except 
the  buccinator  which  also  receives  a  branch  from  the  facial. 
The  internal  maxillary  artery  furnishes  blood. 


286  DESCRIPTIVE  ANATOMY. 


THE  VASCULAR  SYSTEM. 

The  Arteries. 

There  are  two  sets  of  arteries:  one  the  Pulmonary  System, 
the  other  the  Systemic  System.  The  two  systems  communi- 
cate with  one  another. 

In  the  Systemic  circulation,  the  blood  starts  from  the  heart 
in  the  large  arteries,  and  passes  on  into  the  branches  which 
spring-  from  those  arteries,  these  branches  disminishing-in  size 
until  the  capillaries  are  reached.  Returning-,  the  blood  passes 
throug-h  the  veins,  which  increase  in  size  as  we  approach  the 
heart. 

The  Pulrnonary  circulation.  The  heart  is  divided  into  four 
chambers:  two  left,  one  above  and  one  below;  and  two  right, 
one  above  and  one  below.  From  the  chamber  on  the  left,  under 
side,  the  systemic  circulation  starts.  E^ntering  into  the  chamber 
above  on  the  rig-ht  is  the  termination  of  the  venous  system;  and 
from  this  chamber  the  blood  is  poured  into  the  chamber  below 
by  means  of  two  inlets.  From  there  it  passes  down  into  a 
cavity  from  which  the  pulmonary  artery  starts,  this  artery 
breaking-  up  into  two  branches  and  passing-  to  the  lungs.  Af- 
ter making-  the  circuit  of  the  lung-s,  the  blood  is  returned  into 
the  upper  left  side  of  the  heart,  from  which  it  drops  down  into 
the  other  left  cavity,  where  the  aorta  starts. 

The  arteries  all  commence  with  the  one  g-reat  trunk  the  aorta; 
but  for  several  reasons  we  g-enerally  begin  with  one  of  the 
arteries  belong-ing-  to  the   upper  extremity  or  head  and  neck. 

Arteries  decrease  in  size  as  they  throw  off  branches;  but  if 
we  consider  the  combined  area  of  the  two  branches  into  which 
the  artery  is  divided,  we  find  that  this  area  is  g-reater  than 
that  of  the  original  trunk.  Similarly,  if  we  consider  the  com- 
bined area  of  all  the  branches  which  spring-  from  any  g-iven 
artery,  we  find  that  this  area  is  infinitely  g-reater  than  that  of 
the  orig-inal  artery.  On  the  other  hand,  the  combined  area  of 
the  veins,  while   larger  than  the  combined  area  of  the  great 


THE  VASCULAR  SYSTEM.  287 

veins  which  return  the  blood  to  the  heart,  is  much  larg-er  than 
the  combined  area  of  the  arteries.  Consequently,  as  the  blood 
conti'nues  its  course  in  circulating"  throug-h  the  body  the  rapid- 
ity of  the  current  decreases  in  proportion  as  the  distance  from 
the  heart  increases.  As  the  veins  decrease  in  size,  or  contain- 
ing- capacity,  as  they  approach  the  heart,  the  current  becomes 
swifter;  but  never  anything-  like  as  swift  as  the  current  in  the 
arteries. 

In  describing-  an  artery,  we  not  only  g"ive  the  regfion  in  which 
it  lies,  its  course  and  termination;  but  its  relations,  divided  for 
definiteness  of  description  into  muscular,  visceral  and  cord  re- 
lations. Often  these  relations  include  a  vein,  or  another  arter}-^; 
and  there  is  usually  something*  else  to  be  noticed,  for  instance, 
a  tendon.  Besides  that,  arteries  have  other  covering's,  skin 
and  fascia;  and  other  relations,  which  are  neither  cords,  fascias 
nor  muscles.  Such,  for  instance,  are  the  Thyroid  gfland,  the 
Trachea,  the  Pharynx,  or  the  Thymus  g-land.  To  describe 
one,  for  instance,  let  us  take  the  g-reat  vessel  on  the  side  of  the 
neck,  the  Arteria  Innominata.  Starting*  at  the  commencement 
of  the  transverse  aorta,  it  passes  upward  and  outward,  and 
terminates  in  one  of  the  most  frequent  ways  in  which  arteries 
terminate,  viz.,  by  dividing-  into  two  separate  branches:  one 
branch,  the  right  common  carotid,  which  runs  nearly  ver- 
tically upward  in  the  neck,  the  other,  the  rig-ht  subclavian, 
which  apparently  continues  the  course  of  the  orig-inal  vessel, 
with  a  slig-ht  increase  in  its  obliquity.  There  are  two  com- 
Dion  carotids,  di.xid.t'wo  subclavians,  rig-ht  and  left.  To  decide 
the  difference  between  them,  notice  that  the  right  common  carotid 
and  the  rig-ht  subclavian  each  pass  down  into  the  thoracic  cav- 
ity. There  is  a  combination  of  the  two  vessels  on  the  right 
side;  and  no  junction  on  the  leftside,  the  right  springing  by  a 
common  branch,  the  left  by  separate  branches. 

The  Right  Common  Carotid. 

The  rig-ht  common  carotid  artery  differs  from  the  left  in 
that  it  springs  from  the  arteria  innominata,  whereas  the  left 
springs  directly  from  the  arch  of  the  aorta,  hence  the  relations 
of  the  first  portion  of  the  left  common  carotid  would  be  differ- 


288  DESCRIPTIVE  ANATOMY.        ,*, 

ent  from  the  relations  of  the  right  common  carotid  in  this  por- 
tion. The  relations  after  they  have  passed  from  the  thoracic 
cavity,  and  have  reached  the  back  of  the  sterno-clavicular  ar- 
ticulation, become  identical;  and  then  the  description  of  one 
vessel  will  apply  to  the  other. 

The  right  common  carotid  commences  b}''  being-  one  of  the 
two  terminal  branches  of  the  arteria  innominata.  It  then 
passes  upward  witha  slight  inclination  backward  and  outward, 
lying-  upon  the  anterior  tubercles  of  the  transverse  process  of 
the  four  lower  cervical  vertebrae,  about  on  a  line  drawn  from 
the  upper  border  of  the  thyroid  cartilag-e.  After  reaching-  that 
point,  it  terminates  by  dividing-  into  two  branches,  which  are 
known  as  the  internal  and  external  carotid  arteries. 

Covering-  the  vessel  w^e  find,  first,  the  skin  ;  then  a  layer  of 
superficial  cervical  fascia;  then  the  platysmamyoides  muscle; 
then  the  first  layer  of  deep  cervical  fascia  ;  then  the  sterno- 
cleido- mastoid  muscle  ;  then  the  second  layer  of  deep  cervical 
fascia.  After  pulling-  that  aside,  we  come  to  the  sterno-hyoid 
muscle  ;  then  to  the  sterno-thyroid  ;  and  anterior  belly  of 
the  omo-hyoid  ;  then  to  the  last  layer  of  cervical  fascia ; 
forming-  the  front  of  the  sheath  of  the  vessel  behind  ^vhich 
you  have  the  artery  itself. 

It  is  more  convenient  to  divide  the  vessel  into  two  portions, 
the  first  portion  being-  considered  as  lying-  in  the  "Triang-le  of 
Necessity"  or  the  inferior  carotid tricDig-le,  the  second  as  lying- 
in  the  superior,  or  "Triang-le  of  l^lection".  The  first  portion 
commences  as  the  artery  itself  commences,  as  being-  one  of  the 
branches  of  the  arteria  innominata,  and  terminates  where  the 
vessel  is  crossed  by  the  anterior  belly  of  the  omo-hyoid.  The 
second  portion  commences  where  the  first  terminates;  and  ex- 
tends to  the  termination  of  the  artery  at  the  upper  border  of 
the  thyroid  cartilage.  The  first  portion  is  deeply  seated, 
difficult  of  access;  and  the  triangle  is  for  that  reason  known  as 
the  Triangle  of  Necessity.  Throughout  the  first  portion  the 
artery  is  completely  covered  by  the  sterno-cleido-mastoid  mus- 
cles; it  is  only  at  its  commencement  that  it  is  covered  by  the 
sterno-hyoid  and  thyroid,  which  rapidly  draw  away  from  the 
vessel  and  cease  to  be  relations  of  it.     Then  as  we  pass  up  to 


THE  VASCULAR  SYSTEM.  289 

the  seco?id  portion  of  the  vessel  (the  omo-hyoid  being-  the 
dividing"  line,  belongs  partly  to  each  portion),  we  find  that  the 
second  portion  is  covered  by  superficial  and  deep  fascia, 
plat3'snia  myoides,  and  the  sterno-cleido-mastoid,  which  in 
this  situation  overlaps  rather  than  covers.  Throug"hout  its 
entire  course  it  is  covered  by  the  sterno-cleido-mastoid  and  the 
platysma  myoides;  only  at  its  beg^inning-  is  it  covered  by  the 
bellies  of  the  sterno-hyoid  and  sterno-thyroid;  and  only  at  the 
middle  of  its  course  is  it  covered  by  the  omo-hyoid. 

The  more  important  thing's  to  study  in  connection  with  the 
vessel  are  the  cord  relations,  these  being-  always  of  g-reater 
importance  than  anything-  else,  owing-  to  the  dang-er  of  wound- 
ing-. Every  larg-e  artery  protects  itself  by  passing-  as  closely 
as  possible  to  the  bone  ;  but  another  protection  is  the  sheath, 
which  is  formed  of  fibrous  tissue,  in  this  case  a  part  of  the 
deep  cervical  fascia.  So  powerful  is  the  sheath  that  many 
cases  could  be  cited  in  which  vessels  have  been  found  floating" 
in  pus,  the  artery  remaining-  entirely  uninjured.  This  vessel 
possesses  one  of  the  larg-est  sheathes  in  the  body  ;  and  in  the 
same  sheath  with  it  are  found  the  internal  jug-ular  vein  and 
the  pneumog-astric  nerve,  all  lying-  upon  the  same  plane,  the 
artery  being-  most  internal,  the  vein  most  external,  and  the 
nerve  lying-  between  them.  The  nerve  is  sometimes  described 
as  "lying-  between  and  behind"  the  vein  and  artery  ;  but  this 
is  not  correct  :  It  lies  between  them  and  not  behind  them. 
Another  important  structure  running- downward  upon  its  sheath 
is  the  Descendens  noni,  or  Descendens  hypog-lossi.  This 
nerve  passes  downward  on  the  front  of  the  sheath  of  the  com- 
mon carotid:  and  just  before  it  reaches  the  upper  border  of  the 
anterior  belly  of  the  omo-hyoid  it  receives  one  or  two  filaments 
from  the  cervical  plexus  of  nerves  forming-,  just  above  the 
anterior  belly  of  the  omo-hyoid,  Scarpa's  Arch.  In  addition 
there  is  another  important  cord  lying-  just  behind  the  artery, 
which  has  a  larg-e  bulg-e  upon  it  near  its  upper  extremity,  called 
the  cervical  portion  of  the  Sympathetic  nerve.  It  descends 
upon  the  prevertebral  g-roup  of  muscles  directly  behind  the 
sheath. 

Des  Anat— 19 


290  ^DESCRIPTIVE  ANATOMY. 

On  the  upper  portion  of  the  course  of  the  artery  are  g^enerally 
seen  the  superior  thyroid  veins,  frequently  two.  In  the  lower 
portion,  about  its  middle,  are  seen  the  middle  thyroid  gener- 
ally ;  and  below  that  gfenerally  the  anterior  jug-ular,  all  of 
these  veins  being-  superficial.  At  the  commencement  of 
their  course  these  vessels  are  deeply  seated,  and  covered  by  a 
larg"e  number  of  structures  ;  and  they  are  very  close  to  each  > 
other,  the  distance  increasing-  as  we  pass  upward  into  the 
neck.  Owing-  to  the  projection  of  the  Thyroid  cartilag-e, 
with  the  tissues  which  lie  m  the  neig-hborhood  of  it,  these 
vessels  appear  to  be  more  deeply  seated  in  the  second  portion 
than  in  the  beg-inning-  of  their  course.  At  the  commencement 
of  the  artery,  to  its  inner  side,  it  has  the  Trachea  :  passing- 
above,  the  Thyroid  g-land,  passing-  above  that,  the  cartilag-es 
of  the  larynx;  and  then,  still  hig-her  up,  the  side  of  the 
pharynx. 

As  the  Pneumog-astric  nerve  passes  downward,  it  g-ives  off 
an  important  branch,  w^hich  lies  over  the  subclavian  artery,  the 
Recurrent  Laryng-eal.  This  branch  winds  upwards  behind 
the  subclavian  artery,  first  passes  obliquely  inward,  and  then 
passes  behind  the  common  carotid  artery,  and  runs  into 
the  muscles  along-  the  side  of  the  neck.  As  the  nerve  runs 
upward,  it  bears  a  three  fold  relation  to  the  common  carotid 
artery  :  first  behind  and  external,  then  behind  and  then  to  the 
inner  side.  A  branch  of  the  subclavian,  the  inferior  thvroid 
is  also  a  posterior  relation  of  the  first  portion. 

Unlike  nearly  all  arteries,  the  common  carotid  gfives  off  no 
branches  in  its  course.  The  usual  arrang-ement  is  that  the 
arteries  give  off  branches  to  those  structures  among  which 
they  lie.  The  branches  of  one  of  its  terminal  branches  supply 
the  upper  region  of  its  course,  while  the  branches  of  the  sub- 
clavian supply  the  lower  region. 

External  Carotid. 

The  external  carotid  artery,  one  of  the  two  terminal  branches 
of  the  common  carotid,  begins  where  that  artery  bifurcates 
about  on  a  level  with  the  upper  border  of  the  thyroid  cartilage 
and,  continuing  the  direction  of  the  common  carotid,  passes 


THE  VASCULAR  SYSTEM.  291 

beneath  the  posterior  belly  of  the  dig-astric  and  the  stylo-hyold 
muscles,  enters  the  substance  of  the  parotid  g-land  and  termi- 
nates in  that  g-land  behind  the  neck  of  the  condyle  of  the  lower 
jaw  by  dividingf  into  two  branches,  the  temporal  and  the 
internal  maxillary  arteries.  The  temporal  continues  the 
course  of  the  external  carotid  to  mount  over  the  zyg"oma  and 
be  distributed  to  the  side  of  the  head  by  two  branches,  while 
the  internal  maxillary  passes  inward,  behind  the  neck  of  the 
condyle  of  the  lower  jaw  to  supply  the  deep  structures  of  the 
face. 

This  artery  is  divided,  for  convenience  of  description  into 
three  portions. 

Relations. — The  first  portion  of  the  external  carotid  lies  in 
the  superior  carotid  triang-le,  its  length  varying-  as  the  common 
carotid  divides  on  a  level  with,  above  or  below  the  upper 
border  of  the  thyroid  cartilag-e,  for  it  extends  from  the  bi- 
furcation of  the  common  carotid  to  the  stylo-hyoid  and  pos- 
terior belly  of  the  digastric.  It  is  covered  by  the  integument 
and  platysma  and  deep  cervical  fascia,  is  slightly  overlapped 
by  the  sterno-mastoid  and  is  crossed  in  front  by  the  hypo- 
glossal or  twelfth  nerve,  near  the  termination  of  this  portion, 
and  the  lingual  vein  near  its  beginning.  At  its  commence- 
ment the  internal  carotid  lies  to  its  outer  side  ;  but  by  the  time 
the  external  carotid  reaches  the  termination  of  its  first  portion, 
the  internal  carotid  has  passed  behind  it. 

The  second  portion  is  that  which  is  crossed  by  the  stylo- 
hyoid and  posterior  belly  of  the  digastric.  Its  coverings  are 
integument,  platysma,  stylo-hyoid  and  posterior  belly  of  the 
digastric.  The  stylo-glossus  and  pharyngeus  muscles,  glosso- 
pharyngeal and  superior  laryngeal  nerves  cross  between  this 
and  the  internal  -carotid  about  on  a  line  between  the  second 
and  third  portions. 

The  third  ■a^\(S.  last  portion  extends  from  the  stylo-hyoid  and 
posterior  belly  of  the  digastric  to  the  termination  of  the  artery 
behind  the  neck  of  the  condyle  of  the  lower  jaw.  It  lies  embed- 
ded in  the  substance  of  the  parotid  gland  and  is  crossed,  super- 
ficially, near  its  termination,  by  the  facial  nerve  and  the  facial 


292  DESCRIPTIVE  ANATOMY. 

and  temporo-maxillary  veins.  The  first  portion  is  most 
superficial,  the  second  the  shortest  and  the  third  the  long-est 
and  deepest. 

Branches. 

Superior  Thyroid  Occipital" 

Lingual  Posterior  Auricular 

Facial  Ascending-  Pharyng"eal 

Parotid  ean. 

It  should  be  remembered  that  the  common  carotid  gives  off 
no  branches  except  its  terminal  ones  and  hence  the  structures 
in  its  course  have  to  be  supplied  by  other  arteries.  The  ex- 
ternal carotid  does  a  part  of  this  work.  Besides  those  into 
which  it  divides,  the  external  carotid  g-ives  off  six  sing-le  bran- 
ches, and  a  set  to  the  parotid  gland.  The  first  three  arise 
from  the  anterior  aspect  of  the  artery,  low  down  and  in  the 
order  given  from  below  upward.  The  next  two  rise  from  the 
back  of  the  artery  higher  up. 

I.  Superior  Thyroid. 

The  superior  thyroid,  which  is  at  first  very  superficial,  being 
covered  only  by  the  platysma  and  fascia,  forms  a  curve,  first 
passing  upward  and  inward,  then  downward  and  inward, 
crosses  beneath  the  depressor  muscles  of  the  hyoid  bone,  and 
reaches  the  upper  part  of  the  thyroid  gland  to  which  it  is  dis- 
tributed.    It  gives  off  the  following  branches: 

1st.  hyoid,  which  passes  forward  just  beneath  the  hyoid  bone 
to  be  distributed  to  muscles  and  anastomose  with  its  fellow  of 
the  opposite  side. 

2nd.  superior  laryng-eal,  which  passes  forward  on  the  thyro- 
hyoidean  membrane  and  pierces  it  to  be  distributed  to  the 
mucous  membrane  of  the  larynx,  anastomosing  with  Its  fellow. 

3rd.  crico-thyroid,  which  passes  across  the  crico-thyroid 
membrane  and  gives  branches  which  pierce  it  to  reach  the 
mucous  membrane  of  the  larynx  anastomosing  with  its  fellow. 

4th.  muscular  or  superficial  descending  braiich  ^hxch.  passes 
downward  and  outward  across  the  common  carotid  to  supply 
the  sterno-mastoid. 


THE  VASCULAR  SYSTEM.  293 

II.  Lingual. 

The  lingual  arter}^  is  divided  into  four  portions:  1st,  it 
descends  obliquely  inward,  over  the  extremity  of  the  hyoid 
bone  covered  only  by  the  skin  and  platysma;  2d,  it  passes  for- 
ward along-  and  above  the  hyoid  bone,  is  crossed  by  the  digas- 
tric and  then  covered  by  the  hyo-glossus  muscle;  3d,  it  ascends 
to  the  under  aspect  of  the  tongue;  4th,  in  riins  forward  on 
the  under  aspect  of  the  tongue,  under  the  name  of  the  ranine 
artery.  The  first  two  portions  lie  on  the  middle  constrictor 
of  the  pharynx.     Its  branches  are  three: 

1st.  Hyoid,  which  runs  inward  along  the  upper  border  of 
the  hyoid  bone  to  be  distributed  to  muscles  and  anastomose 
with  its  fellow. 

2d.  dorsalis  lingiicc,  which  ascends  to  the  dorsum  of  the 
tongue  along  the  posterior  border  of  the  hyoglossus  muscle  to 
supph^  the  back  of  the  tongue  muscous  membrane  and  soft 
palate. 

3d.  subling-iial,  which  runs  forward  to  the  sublingual  gland 
from  the  margin  of  the  hyo-glossus  and  is  distributed  to  that 
gland,  to  the  mucous  membrane  of  the  mouth  and  to  muscles. 

The  ranine  is  the  terminal  branch  of  the  lingual.  It  passes 
forward  on  the  under  surface  of  the  tongue,  beneath  the  mu- 
cous membrane  is  distributed  to  that  organ  and  anastomoses 
with  its  fellow  at  the  end  of  the  tongue. 

III.  Facial. 

The  facial  artery  arises  just  above  the  hyoid  bone  and  is 
divided  into  two  portions,  one  while  it  is  in  the  neck  and  the  other 
after  it  reaches  the  face.  The  first  portion  passes  forward 
and  upward,  through  the  submaxillary  gland,  to  mount  over  the 
body  of  the  lower  jaw  just  at  the  anterior  inferior  angle  of  the 
masseter  muscle  and  about  one  and  one-half  inches  in  front  of  the 
angle  of  the  lower  jaw.  At  its  origin  it  is  superficial,  being 
covered  only  by  the  skin  and  platysma;  but  it  soon  enters  the 
submaxillary  gland  and  is  crossed  by  the  stylo-hyoid  and  pos- 
terior belly  of  the  digastric.  When  it  leaves  the  gland  and 
mounts  over  the  jaw  it  isagain  superficial,  being  covered  only  by 


294  DESCRIPTIVE  ANATOMY. 

the  integ'ument  and  platysma.  Its  pulsations  can  here  be  felt. 
The  second  portion  of  the  artery  has  a  tortuous  upward  and 
inward  course  over  the  face  towards  the  angle  of  the  mouth, 
thence  along-  the  side  of  the  nose  to  terminate  at  the  inner 
canthus  of  the  eye  as  the  angular  artery.  Its  branches  are 
divided  into  those  g-iven  off  below  the  jaw,  five  in  number, 
and  those  on  the  face,  also  five  in  number.  v 

1st.  inferior  -palatine,  which  ascends  to  the  soft  palate, 
tonsils,  E)ustacian  tube,  stylo-pharyng-eus  and  stylo-g-lossus 
muscles. 

2d.  tonsillar,  which  ascends  to  the  tonsils. 

3d.  submaxillary ,  which  are  from  three  to  five  in  number 
and  ascend  to  the  submaxillary  g-land. 

4th.  submental,  which  runs  forward  beneath  the  lower  jaw 
and  passing-  over  the  symphysis  menti  terminates  by  inoscu- 
lating- w^ith  the  inferior  labial.  It  lies  on  the  mylo-hyoid 
supplies  neig-hboring-  muscles  and  anastamoses  with  the  sub- 
maxillary before  running-  over  the  chin. 

5th.  77iuscular  branches  distributed  to  neig-hboring-  branches. 

The  five  branches  from   the  second  portion  are  as  follows  : 

1st.  inuscular  or  buccal,  which  are  branches  to  adjacent 
muscles. 

2d.  inferior  labail,  which  runs  forward  beneath  the  skin  of 
the  lower  lip,  supplies  muscles  in  its  course  and  anastamoses 
with   the  submental  inferior  coronary  and  the  inferior  dental. 

3rd.  inferior  coronary,  which  skirts  the  edg-e  of  the  lower 
lip,  anastanlose  with  its  fellow  of  the  opposite  side,  with  the 
mental  branch  of  the  inferior  dental  and  with  the  inferior 
labial  and  supplies  muscles  and  g-lands  in  its  course. 

4th.  superior  coronary,  which  skirts  the  edg-e  of  the  upper 
Hp,  giving-  off  a  branch  to  the  septum  of  the  nose,  arteria  septi. 
This  artery  anastamoses  with  its  fellow  and  supplies  struct- 
ures in  its  course.  The  arteria  septi  passes  upward  to  ramify 
on  the  septum  of  the  nose. 

5th.  lateralis  nasi,  which  is  distributed  to  the  side  of  the 
nose,  inosculating-  with  its  fellow  of  the  opposite  side. 

The  angular  artery  is  the  continuation  of  the  facial.    Passing 


THE  VASCULAR  SYSTEM.  295 

up  along-  side  of  the  nose,  it  g-ives  off  small  branches  to  the 
cheek  and  terminates  by  anistaraosing-  with  the  nasal  branch 
of  the  opthalmic. 

The  inferior  labial  and  inferior  coronary  very  frequently 
comes  off  by  a  common  trunk.  Sometimes  it  is  a  common 
trunk  which  divides  into  the  inferior  and  superior  coronary 
arteries. 

IV.  Occipital. 

The  occifiital  branch  of  the  external  carotid  passes  upward 
and  backward  to  the  occipital  g-roove  of  the  temporal  bone, 
beneath  the  muscles  attached  to  the  mastoid  process,  thence 
mounting-  on  the  posterior  aspect  of  the  occipital  bone  and 
piercing-  the  fascia  which  connects  the  cranial  attachment  of 
the  trapezius  with  the  sterno-cleido-mastoid  becomes  superfi- 
cial and  is  distributed  to  the  back  of  the  head.  The  hypog-lossal 
nerve  winds  around,  from  behind  forward — it  crosses  over  the 
internal  carotid  artery,  the  internal  jugular  vein,  the  pneumo- 
gastric  and  spiral  accessory  nerves.     Its  branches  are  : 

1st.  Sterno-mastoid,  which,  sometimes  arising-  directly  from 
the  external  carotid,  descends  to  the  sterno-mastoid  muscle. 

2nd.  muscular  branches  to  stylo-hyoid  and  dig-astric. 

3rd.  two  small  branches  auricular  to  the  concha  and  menin- 
geal to  the  membranes  of  the  brain. 

4th.  f>rinceps  cervicis,  which  passes  down  the  neck  lying- 
deep. 

It  divides  into  a  superficial  branch  which  passes  beneath  the 
splenius  and  inosculates  with  the  superficial  cervical  of  the 
transversus  calli;  and  a  deep  branch  which  passes  beneath 
the  complexus  to  anastomose  with  the  profunda  cervicis. 

V.  Posterior  Auricular. 

The  -posterior  auricular  ya.'^'^^':^  upward  and  backward  behind 
the  ear  and  is  distributed  by  an  aiitcrior  branch  to  the  auricle 
and  by  a  posterior  to  the  back  of  the  head.  It  produces  three 
branches,  the  stylo-mastoid  which  enters  the  stylo-mastoid 
foramen  to  be  distributed  to  the  ear;  the  auricular  which  is 
distributed  to  the  back  part  of  the  cartilag-e  of  the  ear — the 
mastoid  which  passing-  over  the  sterno-mastoid  is  distributed 
to  the  scalp  behind  and  above  the  ear. 


2%  DESCRIPTIVE  ANATOMY. 

VI   Parotidean  Branches. 

T)iQ  parotidean  branches,  four  or  five  in  number,  are  distri- 
buted in  the  parotid  g"land  as  the  external  carotid  is  passing- 
through  it. 

Ascending  Pharyngeal. 

The  ascending-  -pJiaryngeal  branch  spring's  from  the  externa^ 
carotid  just  at  its  origin  and  passes  up  beside  the  pharynx  to 
the  base  of  the  skull,  where  it  divides  into  a  mening-eal  branch 
to  enter  the  cavity  of  the  cranium  throug-h  the  jugular  foramen, 
and  a  pharyngeal  branch  to  adjacent  parts. 

The  Temporal  Artery. 

The  temporal  artery,  one  of  the  two  terminal  branches  of 
the  external  carotid,  begins  where  the  external  carotid  forks 
in  the  parotid  gland,  behind  the  neck  of  the  condyle  of  the 
lower  jaw,  and  emerging  mounts  over  the  zygoma  and  divides 
about  one  and  one-half  inches  above  that  point,  where  it  lies 
on  the  temporal  fascia,  into  an  anterior  and  a  posterior  tempo- 
ral. The  anterior  passes  upward  and  forward,  inosculating 
with  the  frontal  and  supra-orbital  the  posterior  upward  and 
backward  to  be  distributed  to  the  side  of  the  head,  and  to 
inosculate  with  its  fellov/  of  the  opposite  side  and  with  the 
occipital.  These  two  are  called  the  superficial  temporal 
branches  since,  as  will  appear  hereafter,  there  are  other  and 
deeper  temporal  branches. 

It  gives  rise  to  four  branches  besides  those  in  which  it 
terminates. 

1st.  transverse  facial  which  arises  below  the  zygoma,  and 
passes  transversel}"  forward  on  the  masseter  muscle  parallel 
with  Steno's  duct.     It  anastomoses  with  the  facial. 

2nd.  anterior  auricular,  to  the  front  of  the  auricle. 

3rd.  orbital,  which  runs  forward  to  the  outer  angle  of  the 
eye. 

4th.  jniddle  temporal,  which  plunges  into  the  substance 
of  the  temporal  muscle  where  it  is  distributed.  Its  name  is 
derived  from  its  situation  between  the  two  surperficial  tempo- 
ral arteries  and  the  deep  which  spring  from  another  trunk. 


THE  VASCULAR  SYSTEM.  297 

The  Internal  Maxillary. 

The  internal  maxillary  is  the  larg-er  of  the  two  terminal 
branches  of  the  external  carotid.  The  course  of  the  artery  is 
divisible  into  three  portions.  T\\t  first  portio}i  passes  inward, 
forward  and  upward  behind  the  ramus  of  the  inferior  maxilla, 
between  it  and  the  internal  lateral  lig-ament.  The  second 
portion  passes  forward  and  upward  between  the  internal 
pteryg-oid  muscle  within  and  the  temporal  and  masseter  mus- 
cles without.  The  third  portion  disappears  into  the  spheno- 
maxillary   fossa.     Its    branches    are    sixteen    in    number,  as 

follows  : 

First  Portion— Four  Branches. 

1st.  tympanic  which  enters  the  tympanum  throug-h  the 
fissure  of  Glaser. 

2nd.  meniniy-ea  media,  which  ascends  to  enter  the  cavity  of 
the  cranium  throug-h  the  foramen  spinosum. 

It  then  divides  into  an  anterior  and  a  posterior  branch. 
The  anterior  passes  upward  and  forward  over  the  great  wing- 
of  the  sphenoid,  grooves  the  anterior  inferior  angle  of  the 
parietal  and  divides  into  branches  which  rammify  over  the 
dura.  The  posterior  branch  passes  over  the  squamous  por- 
tion of  the  temporal  and  divides  into  branches  on  the  occipital. 
These  branches  anastamose  with  each  other  and  with  the  ante- 
rior and  posterior  meningeal.  They  supply  the  dura  and  the 
bone. 

3rd.  The  mcning-ea  parva,  which  enters  the  cavity  of  the 
cranium  through  the  foramen  ovale. 

4th.  inferior  dental,  which  descends  to  enter  the  dental  fora- 
men of  the  inferior  maxilla  and  runs  forward  in  the  bone 
giving-  a  branch  to  each  fang  of  every  tooth  in  the  lower  jaw. 
Just  before  entering  the  dental  foramen  it  gives  off  a  branch 
called  mylo-hyoidean  ;  and  when  it  reaches  the  mental  fora- 
men it  divides,  sending  a  branch  called  mentalis  through  the 
mental  foramen,  while  another,  called  the  incisive,  continues 
its  course  in  the  bone.  The  mylo-hyoidean  passes  in  the 
groove  of  that  name,  and  supplies  the  mylo-hyoid  muscle. 


298  DESCRIPTIVE  ANATOMY. 

Second  Portion. 

Six  branches  are  derived  from  this  portion  of  the  artery. 
The  deep  temporal,  two  in  number,  occupy  the  anterior  and 
posterior  portions  of  the  temporal  fossa.  They  anastamose 
with  the  superficial  temporal  arteries  and  supply  the  temporal 
muscle.  The  ^/erv^o/rt' branches,  as  the  name  indicates,  su'^- 
ply  the  pteryg"oid  muscles.  The  masseteric  branch  runs 
through  the  sig^moid  notch  and  supplies  the  masseter  from  its 
deep  surface.  The  buccal  passes  forward  between  the  internal 
pterygoid  and  the  lower  jaw  and  supplies  the  buccinator.  It 
anastamoses  with  the  facial. 

Third  Portion. 

1st.  sttjyerior  dental,  which  descends  upon  the  tuberosity  of 
the  superior  maxilla  and  sends  its  branches  through  small 
foramina  in  the  bone  to  supply  the  molar  and  bicuspid  teeth. 

2nd.  Infra-orbital,  which  runs  forward  along  the  canal  in  the 
floor  of  the  orbit,  sending  branches  downward  to  the  front 
teeth  of  the  upper  jaw  and  emerges  through  the  infra-orbital 
foramen  to  supply  adjacent  parts  On  the  face. 

3d.  descending  palatine,  which  descends  along  the  posterior 
palatine  canal  to  emerge  in  the  palate  through  the  posterior 
palatine  foramen  and  send  a  branch  forward  in  a  groove  seen 
on  the  side  of  the  hard  palate(called  the  anterior  palatine  canal) 
which  reaches  the  floor  of  the  nose  through  the  anterior  pala- 
tine foramen. 

4th.  spheno- palatine,  which  enters  the  nose  through  the 
spheno-palatine  foramen  and  divides  into  two  branches,  one  be- 
ing distributed  to  the  septum  and  the  other  to  the  mucous 
membrane  of  the  outer  wall  and  antrum  maxillare. 

5th.  ptergo-palatine,  which  runs  backward  in  the  pterygo- 
palatine canal  to  the  pharynx,  E^ustachian  tube  and  neighboring 
parts. 

6th.  Vidian,  which  passes  backward  along  the  pterygoid 
canal  and,  like  the  preceding,  is  distributed  to  the  mucous 
membrane  of  the  pharynx  and  E)ustachian  tube. 


THE  VASCULAR  SYSTEM.  299 

The  Right  Subclavian. 

The  Rig-ht  Subclavian  artery  is  one  of  the  two  terminal 
branches  of  the  arteria  innominata,  the  other  being-  the  rig-ht 
common  carotid.  It  commences  upon  the  upper  border  of  the 
rig-ht  sterno-clavicular  articulation,  arches  upward  and  out- 
ward, passing-  between  the  Scaleni  muscles;  then  turns  down- 
ward and  outward,  and  terminates  by  becoming- the  axillary  at 
the  junction  of  the  outer  one-third  with  the  inner  two-thirds 
of  the  shaft  of  the  clavicle  on  the  outer  border  of  the  first  rib. 
It  is  thus  seen  that  it  forms  a  bow,  the  hig-hest  part  of  the  arch 
being-  that  which  passes  behind  the  Scaleni  muscles. 

This  warrants  the  sub-division  of  the  artery  into  three 
f>ortions. 

The  -first  commences  by  a  bifurcation  of  the  arteria  innom- 
inata and  terminates  at  the  inner  border  of  the  scalenus  anti- 
cus;  the  second  lies  behind  the  scalenus  anticus;  and  the  third 
portion  extends  from  the  outer  border  of  the  scalenus  anticus 
to  the  termination  of  the  artery  in  the  axilla  at  the  outer  border 
of  the  first  rib.  This  third  portion  is  itself  sometimes  sub- 
divided into  that  part  which  lies  between  the  scalenus  anticus 
and  the  clavicle  and  the  part  which  lies  behind  the  clavicle; 
but  the  division  is  unnecessary. 

Relations.  The  covering-s  of  this  artery  are  the  skin,  su- 
perficial fascia,  platysmamyoides  muscle,  one  layer  of  the  deep 
cervical  fascia,  the  sterno-cleido-mastoid  muscle,  with  the  sec- 
ond layer  of  deep  cervical  fascia,  and  the  posterior  belly  of  the 
omo-hyoid  muscle.  It  is  better  to  take  the  relations  of  the  ar- 
tery as  a  whole;  and  then  consider  them  with  reference  to  the 
various  portions  of  the  vessel.  Thus,  starting-  from  within  and 
passing-  outward  on  the  anterior  face  of  the  artery,  we  find  the 
pneumog-astric  nerve,  with  its  recurrent  laryng-eal  branch,  ex- 
ternal to  that  the  internal  jug-ular  vein,  then  the  phrenic  nerve, 
then  the  scalenus  anticus  muscle,  then  the  suprascapular 
vein  and  artery,  the  nerve  to  the  subclavius  and  the  subclavius 
muscle.  More  superficially,  just  beneath  the  skin,  are  the 
thoracic  branches  of  the  cervical   plexus.     Below    it  are    its 


300  DESCRIPTIVE  ANATOMY. 

vein,  the  recurrent  laryngeal  nerve,  the  lung"  and  pleura,  and 
the  first  rib.  Behind,  the  recurrent  laryngeal,  the  cervical 
portion  of  the  sympathetic  nerve,  the  vertebrae,  the  Scalenus 
anticus  muscle,  and  the  brachial  plexus  of  nerves.  Above, 
the  brachial  plexus  and  the  omo-hyoid  muscle;  and  to  its  inner 
side,  the  right  common  carotid.  . 

To  consider  the  different  parts  separately: 

First  Portion.  The  first  ^orfio)i  is  covered  throughout  by 
the  integument,  platysma,  sterno-cleido-mastoid;  and,  at  its 
commencement,  by  the  right  sterno-clavicular  articulation,  the 
sterno-hyoid  and  sterno- thyroid  muscles.  Superficial  branches 
of  the  cervical  plexus  also  pass  over  it.  Crossing  it  in  front 
are  the  pneumogastric  nerve,  giving  off  here  its  recurrent  laryn- 
geal branch  ;  external  to  this,  the  internal  jugular  vein  ;  and 
external  to  this,  usually,  the  phrenic  nerve.  The  course  of  the 
phrenic  is  downward  and  slightly  inward  upon  the  anterior 
face  of  the  scalenus  anticus  muscle.  Occasionally  it  continues 
on  that  muscle  until  it  passes  beyond  the  artery;  but  generally 
it  drops  off  from  the  muscle  to  the  artery  to  become  an  anterior 
relation  of  the  latter.  In  front  near  its  beginning  is  the  right 
vertebral  vein.  Just  as  the  internal  jugular  vein  crosses  the 
front  of  the  artery  it  communicates  with  the  subclavian  vein 
to  form  the  right  Vena  Innominata.  Hence  the  junction  of 
these  two  veins  would  lie  below  on  a  plane  anterior  and  slightly 
to  the  outer  side  of  the  first  portion  of  the  subclavian.  The 
pneumogastric  here  gives  off  the  recurrent  laryngeal,  which  is 
first  in  front,  then  below,  then  behind  the  artery.  To  the  in- 
ner side  at  its  commencement  is  the  right  common  carotid.  Be- 
hind it  is  the  recurrent  laryngeal,  and  the  cervical  portion  of 
the  sympathetic,  the  cardiac  branches  of  which  cross  its  front. 
Below,  the  artery  rests  upon  the  lung  and  the  pleura.  The 
pleura  of  the  right  side  extends  upward  into  the  root  of  the 
neck  above  the  level  of  the  first  rib,  so  that  the  artery  makes 
an  impression  upon  the  dome  of  the  pleura,  and  a  portion  of 
that  membrane  lies  behind  the  artery  as  well  as  beneath  it. 

The  Second  Portion.  The  second  portion  forms  the  top  of 
the  bow;  and  runs  transversely  outward.  It  runs  behind  the 
Scalenus  anticus  muscle;  and  is  co-extensive  with  its  breadth. 


THE  VASCULAR  SYSTEM.  301 

In  front  are  the  inteofument  superficial  fascia,  the  platysma 
first  layer  of  deep  cervical  fascia,  the  sterno-cleido-mistoid 
second  layer  of  deep  cervical  fascia,  with  branches  of  the  cer- 
vical plexus  extending-  over  the  clavicle.  Occasionally  on  its 
front  is  the  phrenic  nerve.  The  suprascapular  artery  and  the 
transversa  colli  branches  of  the  subclavian  pass  across  the  front 
of  the  scalenus  anticus  muscle;  and  should  be  considered  in  all 
operations  in  this  situation.  The  brachial  plexus  of  nerves  lies 
behind  and  above  the  artery,  separating-  it  from  the  scalenus 
posticus  muscle.  Below  and  behind  are  found  the  pleura  and 
the  lung-s.  The  subclavian  vein  is  not  a  relation  of  the  artery, 
lying-  some  distance  below  it  and  separated  from  it  by  the 
scalenus  anticus. 

The  Third  Portion.  The  third  portion  is  the  downward 
and  outward  part,  extending-  from  the  outer  edge  of  the  Scale- 
nus anticus  to  the  outer  border  of  the  first  rib,  and  lying-  in 
its  lower  portion  between  the  clavicle  and  the  first  rib.  It  is 
covered  entirely  by  the  platysma  ;  and  to  a  slig-ht  extent,  in 
many  cases,  by  the  outer  edg-e  of  the  sterno-cleido-mastoid  ; 
and,  in  a  few  cases,  where  this  muscle  has  a  redundant  orig-in, 
the  third  portion  of  the  artery  is  covered  completel}^  by  it. 
The  artery  lies  in  the  triangular  space  bounded  above  b}^  the 
omo-hyoid,  internally  by  the  sterno-cleido-mastoid,  and  below 
by  the  clavicle.  This  space  is  covered  over  by  a  rather  dense 
layer  of  the  deep  cervical  fascia,  which  is  of  course  one  of  the 
coverings  of  the  vessel.  Crosssing-  in  front  of  it  are  the  supra- 
scapular artery,  a  branch  of  the  subclavian  itself,  which  passes 
outward  just  beneath  the  upper  border  of  the  clavicle.  This 
artery  is  accompanied  by  its  own  vein.  Crossing-  the  front  of  it 
from  above  is  the  external  jug-ular  vein,  which  descends  the 
neck  lying-  just  behind  the  outer  edg-e  of  the  sterno-cleido- 
mastoid  muscle  ;  and,  after  having  received  on  the  front  of 
the  artery  the  suprascapular  and  tran verse  veins,  it  terminates 
in  the   subclavian   on   the  outer   side  of  the  scalenus  anticus. 

The  subclavius  muscle,  the  descending-  branches  of  the  cer- 
vical plexus,  and  the  nerve  to  the  sub-clavius  muscle  are  also 
in  front.  Owing-  to  the  curve  in  the  course  of  the  artery, 
what  has  heretofore  been  called  its  upper  aspect  now  becomes 


302  DESCRIPTIVE  ANATOMY. 

its  external.  The  brachial  plexus  of  nerves  has  been  described 
as  being  an  external  relation,  though  the  plexus  lies  on  a 
plane  posterior  to  the  artery  as  well  as  to  its  outer  side. 
The  omo-hyoid  lies  above  and  to  the  outer  side,  in  front  of  the 
plexus.  To  the  inner  side  is  the  subclavian  vein,  which,  is  in 
contact  with  the  vessel  for  only  a  short  distance  before  its  ter- 
mination. The  vein,  it  will  be  observed,  is  a  relation  of  the 
iirst  and  third  portions  only  ;  that  is,  it  is  in  contact  with  the 
outer  front  aspect  of  the  first  portion  at  its  commencement, 
and  with  the  inner  front  aspect  of  the  third  portion  at  its  ter- 
mination, bearing  no  relation  to  the  second  portion,  hence  it 
presents  the  same  relation  which  a  string  bears  to  a  bent  bow. 
At  the  very  commencement  of  this  portion  it  lies  upon  the 
pleura,  so  that  it  will  be  seen  that  the  pleura  lies  below  and 
behind  all  three  of  the  portions  of  the  artery,  though  for  the 
third  portion  the  relation  is  only  a  momentary  one,  the  first 
rib  quickly  separating  the  two  structures.  The  lig-ation  of 
this  vessel  is  preferably  performed  in  the   third    portion  of  its 

course. 

Branches. 

Vertebral 
(  Inferior  Thyroid         Internal  Mammary 
Thyroid  Axis  <  Suprascapular  Superior  Intercostal 

(  Transversa  Colli         Profunda  Cervicis. 

These  seven  branches  usually  rise  by  four  trunks:  the  ver- 
tebral, thyroid  axis,  internal  mamary,  and  the  common  trunk 
for  the  superior  intercostal  and  cervicalis  profunda. 

Vertebral. 

The  vertebral  is  the  first  and  largest  branch  of  the  subclav- 
ian. It  arises  from  the  posterior  aspect  of  the  first  portion  of 
the  artery;  and  enters  the  foramen  in  the  transverse  process  of 
the  sixth  cervical  vertebra,  usually.  Occasionally  it  passes  to 
the  fifth;  but,  though  the  seventh  is  perforated,  the  vertebral 
artery  never  enters  it.  It  passes  upward  through  the  fora- 
mina of  the  transverse  process,  winds  backward  around  the 
superior  articular  process  of  the  atlas,  enters  the  cavity  of  the 
cranium  through  the  foramen  magnum,  and  at  the  lower  bor- 


THE  VASCULAR  SYSTEM.  303 

der  of  the  pons  Varolii  unites  with  its  fellow  of  the  opposite 
side  to  form  a  sinsfle  trunk,  called  the  Basilar  artery,  which 
runs  upward  and  forward  to  the  anterior  border  of  the  pons, 
where  it  divides  into  four  terminal  branches,  two  on  either 
side.  At  its  orig-in  the  internal  jugular  vein  and  the  infe- 
rior thyroid  artery  lie  in  front  of  it.  On  the  left  side,  while 
l\4no-  between  the  scalenus  anticus  and  longus  coli  muscles, 
the  thoracic  duct  passes  in  front  of  it.  Besides  its  terminal 
branches  it  g-ives  off  the  following-  branches  : 

1st.  lateral  spinal,  which  are  g^iveu  off  as  the  artery  ascends 
the  neck  to  enter  the  intervertebral  foramina.  They  there 
divide  into  two  branches:  one  for  the  bodies  of  the  vertebrae, 
and  the  other  for  the  spinal  cord  and  its  membranes.  That  for 
the  spinal  cord  reaches  its  along-  the  roots  of  the  spinal  nerves, 
while  the  branch  for  the  bodies  of  the  vertebrae  divides  into 
an  ascending-  and  a  descending-  branch,  anastomosing-  with 
similar  branches  coming-  from  above  and  below. 

2nd.  The  muscular  branches  are  unimportant.  They  come 
from  the  lower  portion  of  the  artery,  and  are  distributed  to 
the  cervical  muscles. 

3d.  Tho. posterior  meningrcal  are  small  branches  distributed 
to  the  dura  mater  of  the  cranium. 

4th.  The  anterior  spinal  zx\'$,q's,  near  the  termination  of  the 
vertebral,  unites  with  its  fellow  of  the  opposite  side,  and  passes 
downward  on  the  middle  of  the  spinal  cord,  where  it  receives 
communications  from  the  lateral  spinal  branches,  before  men- 
tioned, and  forms  a  continuous  vascular  channel  down  the 
anterior  aspect  of  the  cord. 

5th.  The  posterior  spinal  winds  around  the  medulla,  unites 
with  its  fellow  of  the  opposite  side,  passes  down  behind 
the  posterior  roots  of  the  spinal  nerves,  and  receives  similar 
branches  from  the  lateral  spinal.  This  also  forms  a  branch 
passing-  down  the  spinal  cord. 

<)th.  ^\\Q.  posterior  inferior  ce7'ebellar  7vc\v,^'s>  just  before  the 
termination  of  the  vertebral;  and  passing-  across  the  lateral  as- 
pect of  the  medulla,  winds  around  the  inferior  portion  of  the 
cerebellum,  to  which  it  is  distributed. 


304  DESCRIPTIVE  ANATOMY. 

Basilar. 

The  Basilar  ?ivX.Qry  is  formed  by  the  junction  of  the  two  ver- 
tebral arteries  above  the  middle  of  the  medulla  oblongata;  and 
after  passing-  upward  on  the  lower  surface  of  the  pons  varolii, 
it  terminates  on  the  upper  border  of  that  body  by  dividing  into 
two  branches,  the  posterior  cerebral  arteries.  It  gives  off  the 
following  branches: 

1st.  transverse,  which  are  numerous  small  branches  given 
off  to  each  side  of  the  pons  Varolii. 

2nd.  anterior  inferior  cerebellar,  or  anterior  cerebellar,  which 
arises  soon  after  the  origin  of  the  basilar;  and  passing  across 
the  pons  a  little  below  its  centre,  reaches  the  anterior  border 
and  lower  surface  of  the  cerebellum,  where  anastomosing  with 
the  posterior  inferior  cerebellar,  it  is  distributed  to  that  organ. 
It  is  in  reality  scarcely  more  than  one  of  the  transverse  branches. 

In  addition  to  these  way-side  branches,  the  basilar  artery 
gives  off  the  following  terminal: 

1st.  superior  cerebellar,  which  passing  across  the  upper 
border  of  the  pons,  passes  into  the  fissure  between  the  upper 
border  of  the  cerebellum  and  the  cerebrum,  and  ramifies  upon 
the  upper  surface  of  the  cerebellum. 

2nd.  T\\Qj^osterior  cerebral  also  winds  around  the  outer  bor- 
der of  the  pons,  passing  to  the  inner  surface  of  the  posterior 
lobe  of  the  cerebrum,  to  which  it  is  distributed,  anastomosing 
with  the  other  cerebral  arteries. 

These  two  vessels  are  formed  by  the  bifurcations  of  the  bas- 
ilar artery,  which  just  before  it  divides,  gives  off  numerous 
small  branches,  which  enter  the  minute  foramina  constituting 
the  locus  ^erforatus  at  the  base  of  the  brain. 

Thyroid  Axis. 
The  Thyroid  Axis  is  a  short  thick  trunk,  which  arises  from 
the  upper  portion  of  the  subclavian,  just  at  the  inner  border  of 
the  scalenus  anticus  muscle.  It  almost  immediately  divides 
into  three  branches  ;  the  Inferior  Thyroid,  the  Suprascapular, 
and  the  Transversa  Colli. 


THE  VASCULxVR  SYSTEM.  •  305 

Inferior  Thyroid. 

The  inferior  thyroid,  the  branch  from  which  the  plexus  re- 
ceives its  name,  first  passes  vertically  upward  for  a  distance  of 
an  inch  and  one-half  or  two  inches.  It  then  turns  inward,  cross- 
es behind  the  sheath  of  the  common  carotid  artery  to  reach 
the  thyroid  gland.  It  gives  off  branches,  or  twigs,  called 
lary)i§eal,  tracheal,  and  ocsopliag-cal,  which  are  distributed  to 
the  structures  named:  the  larynx,  the  trachea  and  the  oesopha- 
gus. Just  as  it  makes  its  transverse,  horizontal  turn  there 
springs  off  a  large  branch,  called  the  cervicalis  ascendens, 
which  passes  upward  on  the  anterior  tubercles  of  the  transverse 
processes  to  be  distributed  to  muscles  and  glands  in  the 
neck. 

Suprascapular. 

The  suprascapular,  the  next  most  constant  branch,  passes 
outward  across  the  scalenus  anticus  muscle,  where  it  is  a  dis- 
tant relation  of  the  second  portion  of  the  subclavian.  It  then 
turns  downward  until  it  reaches  the  clavicle,  behind  which  it 
passes  outwafd  over  the  scapula,  crossing  in  its  course  the 
third  portion  of  the  sudclavian.  It  passes  over  the  transverse 
ligament  of  the  scapula  to  reach  its  dorsum  in  the  supraspinous 
fossa,  where  it  gives  off  branches  to  the  bone,  to  the  supra- 
spinatus  muscle,  and  a  branch  which  winding  around  the  an- 
terior border  of  the  spine,  enters  the  infraspinous  fossa,  to 
communicate  with  vessels  in  that  situation,  chiefly  the  dorsalis 
scapula?  branch  of  the  axillary. 

Transversa  Colli. 

Next  to  the  inferior  thyroid,  the  transversa  colli  is  the  larg- 
est of  the  branches  of  the  thyroid  axis,  and  the  least  frequent 
of  its  progeny.  It  passes  across  the  side  of  the  neck  over  the 
scalenus  anticus  muscle,  above  the  level  of  the  second  portion 
of  the  subclavian,  very  frequently  passing  between  some  of 
the  cords  of  the  brachial  plexus  of  nerves.  On  reaching  the 
anterior  edge  of  the  trapezius  it  divides  into  two  branches:  the 
cervicalis  superjicialis  and  tlie  posterior  scapular.     The  cer- 

Des  Anat— 20 


306  DESCRIPTIVE  ANATOMY. 

vicalis  sti-perficialis  runs  upward  to  anastomose  with  the 
superficial  branch  of  the  arteria  princeps  cervicis  from  the  oc- 
cipital. The  -posterior  sca-piilar,  much  larger  than  the  preced- 
ing-, passes  to  the  vertebral  border  of  the  scapula;  and  des- 
cending along  it,  anastomoses  with  the  dorsalis  scapula 
branch  from  the  subscapular  artery. 

Internal  Mammary. 

The  internal  mammary  arises  from  the  lower  aspect  of  the 
subclavian  at  the  inner  edge  of  the  scalenus  anticus,  and  fre- 
quently directly  opposite  the  origin  of  the  vertebral.  It  passes 
downward  upon  the  costal  cartilages  about  half  an  inch  from 
the  edge  of  the  sternum  to  the  diaphragm,  where  it  divides 
into  its  two  terminal  branches  :  the  su-perior  epigastric  and 
mtisculo-phrenic.  It  is  accompanied  by  satellite  veins,  lying 
upon  either  side.  At  its  origin  it  is  covered  by  the  internal 
jugular  and  sub-clavian  veins,  and  has  crossing  it  the  phrenic 
nerve.     Its  branches  are  : 

1st.  The  comes  nervi  -phrenici,  which  arises  at  the  upper 
portion  of  the  vessel.  It  is  a  long  and  slender  branch  ;  and 
accompanies  the  phrenic  nerve,  having  the  same  relations  as 
that  nerve,  and  terminates  by  anastomosing  w^ith  the  other 
arteries  of  the  diaphragm. 

2nd.  The  anterior  intercostal,  which  are  given  off  to  the 
intercostal  spaces,  over  which  the  internal  mammary  passes. 
Kach  passing  outward,  soon  divides  into  two  branches,  one 
for  the  upper  and  the  other  for  the  lower  border  of  the  edges 
of  the  ribs.  These  branches  occasionally  spring  separately 
from  the  artery.  They  first  lie  between  the  intercostal  mus- 
cles and  the  pleura  ;  and  then  between  the  two  intercostal 
muscles. 

3rd.  perforating-  branches.  These  are  usually  six  in  num- 
ber, corresponding  to  the  number  of  intercostal  spaces.  They 
pass  forward  to  the  front  of  the  thorax ;  then  running 
outward,  are  distributed  to  the  muscles,  and  in  the  female, 
chiefly  to  the  mammary  gland. 

4th.  The  mediastinal,  small  and  unimportant  branches, 
which  supply  the  structures  of  the  anterior  mediastinum. 


THE  VASCULAR  SYSTEM.  307 

5th.  Pericardiac  bra)iches,  which  are  about  the  size  of  the 
mediastinal  and  are  distributed  to  the  pericardium. 

These  are  the  way-side  branches  of  the  vessel.  Of  the  two 
terminal  branches,  the  larg-er,  the  superior  epig-astric,  leaves 
the  thoracic  cavit}"  behind  the  seventh  costal  cartilage.  It  en- 
ters the  sheath  of  the  rectus  muscle;  and  continuing"  its  course 
downward,  anastomoses  with  the  inferior  epigastric,  a  branch 
which  springs  from  the  external  iliac.  This  is  the  longest 
anastomosis  in  the  body,  establishes  a  connection  between  the 
arteries  in  the  upper  and  the  arieries  in  the  lower  extremity, 
and  renders  it  conceivable  that  the  abdominal  aorta  might  be 
ligated  without  immediate  death.  It  gives  off  branches  to  the 
muscles  in  its  course. 

The  miisculo-phrenic  follows  the  curvature  of  the  lower 
ribs.  It  passes  downward  and  outward,  giving  off  intercostal 
branches  similar  to  those  given  off  from  the  trunk  of  the  inter- 
nal mammary  itself,  and  performing  the  same  service,  and  in 
addition  giving  off  a  branch  to  the  diaphragm. 

Superior  Intercostal. 

The  superior  intercostal  and  profundus  cervicis  usually 
spring  by  a  common  trunk  from  the  second  portion  of  the 
subclavian  artery,  though  occasionally  they  rise  from  the  third 
portion,  and  occasionally  by  separate  trunks.  The  superior 
intercostal  curves  backward  from  the  apex  of  the  pleura  until 
it  reaches  the  head  of  the  first  rib,  when  it  changes  its  direc- 
tion, and  supplies  the  first  intercostal  space  after  the  manner 
of  all  intercostal  arteries. 

Profundus  Cervicis. 

The  profundus  cervicis  passes  backward  between  the  trans- 
verse process  of  the  seventh  cervical  vertebra  and  the  first 
rib,  or  occasionally  the  transverse  process  of  the  first  dorsal 
vertebra,  and  passes  upward  in  the  neck  to  inosculate  with  the 
deep  division  of  the  princeps  cervicis  branch  of  the  occipital 
artery,  establishing  a  collateral  circulation  between  the  carotid 
and  the  subclavian  arteries. 

The  Axillary  Artery. 

The  Axillary  is  the  second  sub-division  of  the  artery  of  the 


308  DESCRIPTIVE  ANATOMY. 

Upper  extremity.  It  beg-ins  by  being  a  continuation  of  the 
subclavian  where  that  artery  ceases  at  the  outer  border  of  the 
first  rib,  passes  downward  and  outward  from  the  upper  lateral 
aspect  of  the  chest,  corresponding-  to  the  first  four  ribs,  and 
down  the  inner  aspect  of  the  arm  to  terminate  at  the  lower 
border  of  the  tendons  of  the  latissimus  dorsi  and  teres  major 
muscles  by  becoming  the  brachial  artery.  The  direction  of 
the  artery  will  of  course  vary  with  the  position  of  the  limb; 
and  its  relations  are  studied  with  the  limb  in  the  anatomical 
position. 

Relations.  The  artery  is  covered  throughout  by  the  pecto- 
ralis  major,  and  through  part  of  its  extent  by  the  pectoralis 
minor,  and  of  course  by  the  skin,  superficial  and  deep  fascias. 
Throughout  its  course  its  vein  lies  to  its  inner  front  aspect. 
The  brachial  plexus  of  nerves  is  a  continuous  relation,  lying 
to  its  outer  side  in  the  beginning,  on  all  three  sides  in  the  sec- 
ond portion  of  its  course,  while  the  terminal  branches  bear 
various  relations  to  the  third  portion  of  the  artery.  The  rela- 
tionship to  the  pectoralis  minor  warrants  the  subdivision  of 
the  vessel  into  three  portions,  each  of  which  should  be  studied 
in  detail.  ^\lq,  first  -portion  extends  from  the  beginning  of  the 
vessel  to  the  upper  border  of  the  Pectoralis  minor  muscle;  and 
is  contained  in  the  triangular  space  bounded  above  by  the 
clavicle,  below  by  the  pectoralis  minor,  and  externally  by  the 
humerus.  The  second  -portion  commences  at  the  upper  bor- 
der of  the  pectoralis  minor,  and  terminates  at  its  lower  border 
by  becoming  the  third  portion.  The  third  portion,  commenc- 
ing at  the  lower  border  of  the  pectoralis  minor,  terminates  at 
the  lower  border  of  the  tendons  of  the  latissimus  dorsi  and 
teres  major  by  becoming  the  brachial  artery. 

First  Portion.  The  first  portion  is  covered  by  the  skin, 
superficial  and  deep  fascia,  and  the  pectoralis  major  muscle. 
It  is  crossed  by  the  costo-coracoid  membrane  ;  and  by  the 
outer  anterior  thoracic  nerves,  and  the  acromio-thoracic  and 
cephalic  veins.  Internally  it  has  the  second  serration  of  the 
Serratus  magnus,  the  first  rib,  and  the  first  intercostal  muscle. 
Behind,  it  lies  upon  the  tendon  of  the  subscapularis.  Its  vein 
is  internal  and  in  front ;  while  the   brachial  plexus   of  nerves 


THE  VASCULAR  SYSTEM.  309 

lies  to  its  outer  side  and  slio-htly  above  it.  More  superficially, 
in  the  interval  between  the  pectoralis  major  and  the  deltoid,  it 
is  crossed  by  the  cephalic  vein.  Behind  it  is  the  respiratory 
nerve  of  Bell. 

Second  Portion.  The  second  portion  is  covered  by  the  skin, 
superficial  and  deep  fascias,  pectoralis  major  and  pectoralis 
minor.  This  is  the  portion  crossing-  from  the  chest  to  the 
arm  ;  and  corresponds  to  the  position  of  the  third  serration 
of  the  serratus  mag-nus.  Behind,  it  rests  upon  the  subscapu- 
laris.  The  cords  of  the  brachial  plexus  are  here  divided  into 
three  :  internal,  external,  and  posterior,  which  bear  the  corres- 
ponding- relations  to  the  second  portion  of  the  axillary,  while 
the  vein  is  still  internal  and  anterior. 

Third  Portion.  The  third  portion  is  covered  by  the  pecto- 
ralis major,  and  a  strong-  fascia,  which  covers  over  the  axillary 
space.  Posteriorly  it  rests  upon  the  tendons  of  the  latissimus 
dorsi  and  teres  major  and  subscapularis  muscles,  while  exter- 
nal to  it  is  the  coraco-brachialis  and  the  short  head  of  the  biceps. 
At  the  beg-inning-  of  this  portion  the  brachial  plexus  breaks  up 
into  its  terminal  branches;  and  all  of  these  branches  bear  some 
relation  to  the  vessel.  On  the  front  of  its  commencement  the 
external  and  internal  cords  each  g"ive  off  a  branch,  which  unite 
to  form  the  median  nerve.  This  nerve  immediately  drops  to 
the  outer  side  of  the  vessel;  and  maintains  that  relation  to  its 
termination.  The  outer  cord  also  g-ives  off  the  musculo-cutane- 
ous,  which  is  an  external  relation  for  a  short  distance,  then, 
plung-ing-  into  the  fibres  of  the  coraco-brachialis,  ceases  to  be  a 
relation  of  the  axillary.  The  inner  cord,  after  contributing- 
one  root  to  the  median,  g-ives  off  the  ulna  and  internal  cutaneous 
nerves,  both  of  which  are  fixed  internal  relations.  To  the  in- 
ner front  aspect  is  the  vein.  Behind,  it  rests  upon  the  circum- 
flex nerve  and  the  subscapular  artery  for  a  short  distance,  while 
the  last  cord  of  the  plexus,  the  musculo-spiral,  is  a  continuous 
posterior  relation. 

The  Branches. 
Short  Thoracic  Long-  Thoracic 

Acromial  Thoracic  Subscapular 

Thoracica  Alaria  Posterior    Circumflex 

Anterior  Circumflex 


310  DESCRIPTIVE  ANATOMY. 

The  point  of  orig-in  of  the  brcDiches  of  the  axillary  is  very 
uncertain,  and  no  perfectly  accurate  description  applying- to  all 
cases  can  be  written.  Usually  the  short  thoracic  and  the  acro- 
mial thoracic  arise  from  the  first  portion,  the  thoracica  alaria 
and  long-  thoracic  from  the  second,  and  the  subscapular  and 
anterior  and  posterior  circumflex  from  the  third.  Sometimes 
they  will  rise  by  common  branches  ;  and  almost  any  arrang-e- 
ment  may  be  anticipated  in  the  orig-in  of  the  branches  of 
this  vessel. 

Short.  Thoracic. 

The  5/zorz' //^or«c:^'<;  usually  arises  by  a  common  trunk  with 
the  acromial  thoracic.  It  passes  inward  along-  the  upper  bor- 
der of  the  pectoralis  minor,  then  between  the  two  pectoral 
muscles  to  be  distributed  to  the  upper  intercostal  muscles  and 
a  part  of  the  serratus  mag-nus,  anastomosing-  with  the  inter- 
costal arteries.  It  frequently  sends  branches  to  the  pectoral 
muscles,  and  occasionally  to  the  mammary  g-land. 

Acromial  Throacic. 

The  acromial  thoracic,  usually  arising-  by  a  common  trunk 
with  the  short  thoracic,  arises  just  above  the  pectoralis  minor, 
passes  directly  forward  to  pierce  the  costo-coracoid  membrane, 
and  divides  into  three  branches,  which  from  their  distribution 
have  been  called  the  acromial,  the  -pectoral,  and  the  descending" 
thoracic. 

1st.  The  ^^dT^ora/ passes  between  the  pectoralis  major  and 
minor,  and  is  distributed,  in  the  main,  to  the  mammary  g-land, 
some  branches  g'oing  to  the  pectoral  muscles. 

2nd.  The  acromial,  thoug-h  the  smallest  branch,  g-ives  its 
name  to  the  trunk,  and  passes  outward  across  the  coracoid 
process,  sometimes  piercing-  the  deltoid  muscle,  where  it 
anastomoses  with  the  circumflex  and  suprascapular  arteries, 
forming-  the  plexus  around  the  acromion  process. 

3d.  The  descending- branch  passes  into  the  interval  between 
the  deltoid  and  pectoralis  major  muscles,  and  is  distributed  to 
the  muscles  in  its  course,  anastomosing  with  the  plexus  formed 
by  the  preceding-  branch. 

The  thoracica  alaria  are  not  infrequently  branches  from  the 


THE  VASCULAR  SYSTEM.  311 

long- thoracic.  They  sometimss  arise  separately  from  the  trunk; 
and  are  distributed  miinly  to  the  lymphatics,  integument  and 
fascia  of  the  axilla. 

TaQlo}io  thoracic  arises  either  alone,  or  by  a  common  trunk 
with  the  preceding-,  pissing-  between  the  pectoral  muscles  and 
the  serratus  magnus  to  reach  the  lateral  aspect  of  the  chest. 
It  g-ives  branches  to  the  pectorals  and  to  the  serratus  magnus, 
anastomoses  with  the  intercostal  arteries,  and  occasionally  gives 
a  large  branch  to  the  mammary  gland. 

The  subscapular  is  usually  the  largest  branch  of  the  axil- 
lary artery,  arising  generally  oppDsite  the  lower  border  of 
the  subscapularis.  It  runs  downward  and  inward,  following 
the  edge  of  that  muscle,  supplies  it,  the  teres  major,  the 
latissimus  dorsi,  anl  serratus  mignus,  and  gives  branches  to 
structures  in  the  axillary  space.  At  the  inferior  angle  of  the 
scapular  it  anastomoses  with  the  posterior  scapular,  while  the 
branches  which  pass  to  the  thoracic  wall  anastomose  with  the 
intercostal  and  long  thoracic  arteries.  From  an  inch  to  an 
inch  and  one-half  after  its  origin  it  gives  off  a  large  branch, 
called  the  dorsalis  scapula: ,  which  passing  through  the  triangu- 
lar space  between  the  teres  major  below,  the  teres  minor  above, 
and  long  head  of  the  triceps  externally,  curves  around  the 
axillary  border  of  the  scapula,  and  reaches  the  infraspinous 
fossa,  where  it  is  distributed  to  that  fossa  and  to  the  infraspi- 
natus muscle,  anastomosing  with  the  suprascapular  and  the 
posterior  scapular  arteries.  It  also  supplies  the  teres  minor, 
and  sometimes  gives  a  branch  to  the  teres  major  muscle. 

The  anterior  circumflex,  a  very  small  vessel,  frequently 
arises  by  a  common  trunk  with  the  posterior,  or  it  may  arise 
from  the  subscapular.  It  pisses  beneath  the  coraco-brachialis 
and  short  head  of  the  biceps  muscle,  passes  over  the  bicipital 
groove  ;  and  gives  off  a  branch  to  the  shoulder  joint,  while 
the  remainder  of  the  artery  winds  around  the  neck  of  the 
humerus,  and  anastomoses  with  the  posterior  circumflex. 

The  posterior  circumflex,  quite  a  large  ve^isel,  arises  from 
the  third  portion  of  the  axillary  below  the  subscapularis  muscle, 
pisses  through  the  quadrilateral  spice  bounded  externally  by 
the  shaft  of  the   humerus,  internally  by  the  long   head   of  the 


312  DESCRIPTIVE  ANATOMY. 

triceps,  above  by  the  teres  minor,  below  by  the  teres  major, 
winds  around  the  back  of  the  humerus,  and  passing  beneath 
the  deltoid,  breaks  up  into  a  largfe  number  of  branches,  to  be 
distributed  to  that  muscle  throug-hout  its  deep  surface.  In 
addition  to  this  work,  it  gives  off  branches  to  the  head  of  the 
humerus  and  the  shoulder  joint,  and  some  axillary  branches, 
while  the  continuation  of  the  artery  anastomoses  with  the  an- 
terior circumflex,  completing-  the  vascular  zone  around  the  up- 
per extremity  of  the  humerus. 

Frequently  this  artery  arises  by  a  common  trunk  with  the 
anterior  circumflex,  each  artery  then  pursuing"  its  usual 
course.  The  two  anastomose  with  each  other,  with  the  supra- 
scapular and  the  dorsalis  scapulse,  thus  establishing- a  complete 
arterial  zone  around  the  shoulder. 

Brachial  Artery. 

The  brachial  is  the  third  subdivision  of  the  artery  of  the 
upper  extremity.  It  beg^ins  by  being-  a  continuation  of  the 
axillary  at  the  lower  border  of  the  tendons  of  the  latissimus 
dorsi  and  teres  major  and  passing-  downward  and  outward 
terminates  half  an  inch,  or  a  fing^er's  breadth,  below  the  middle 
of  the  front  of  the  elbow-joint  by  dividing-  into  the  ulnar  and 
radial  arteries.  It  lies  first  on  the  inner  side  of  the  arm  and 
then  on  the  front,  so  that  in  order  to  check  the  circulation  by 
pressure  ;  in  the  first  part  of  its  course  the  force  must  be  di- 
rected outward  and  backward  and  in  the  second  part  directl}^ 
backward. 

Relations. — The  muscular  relations  are  as  follows:  To  its 
outer  side,  at  first,  is  the  lower  half  of  the  coraco-brachialis 
and  when  this  relation  is  lost  by  the  insertion  of  the  muscle, 
its  place  is  taken  by  the  biceps,  whose  belly,  when  the  muscle 
is  bulky,  overlaps  the  artery.  At  the  bend  of  the  elbow  it  lies 
beneath  the  slip  given  ofl"  by  the  biceps.  In  the  first  part  of 
its  course  it  lies  on  the  internal  intermuscular  septum  which 
separates  it  from  the  inner  head  of  the  triceps,  and  in  the  lower 
part  on  the  brachialis  anticus. 

Its  relations  to  cords  are  as  follows: 

It  is  accompanied  by  satellite  veins,  one  on  either  side,  the 
one  on  the  inner  side  being-  the  larger. 


THE  VASCULAR  SYSTEM.  313 

To  its  inner  side  are  the  basilic  vein  and  the  internal  cuta- 
neous nerve.  Both  vein  and  nerve  are  at  first  beneath  the  in- 
vesting fascia  of  the  arm;  but  as  the  structures  pass  downward, 
they  both  become  superficial  and  are,  consequently,  internal 
to  and  in  front  of  the  artery. 

The  median  nerve  lies  first  to  the  outer  side  of  the  arter}', 
then  crosses  it,  usually  in  front,  about  the  middle  of  the  arm 
and  reraai-ns  a  continuous  internal  relation. 

The  ulna  nerve  is  a  postero  internal  relation  of  the  brachial 
for  the  upper  one-half  of  its  course,  when  it  leaves  that  artery 
to  pass  to  the  back  of  the  elbow  joint.  For  a  few  inches  the 
inferior  profunda  artery,  accompanying"  the  ulna  nerve,  bears 
also  a  posterior  relation  to  the  brachial.  The  musculo-spiral 
nerve  and  the  superior  profunda  artery  are  momentary  poste- 
rior relations  above. 

Brachial  at  the  Elbow. 

These  relations  are  of  such  importance  that  the}^  must  be 
g-iven  separately.  It  lies  on  the  middle  of  the  front  of  the 
joint  with  a  satellite  vein  on  either  side.  On  its  outer  side  is 
the  tendon  of  the  biceps  muscle;  on  its  inner  side  the  median 
nerve.  In  front  of  it  is  the  bicipital  fascia  and  upon  that  fascia 
are  found  the  terminal  branches  of  the  internal  cutaneous  nerve 
and  the  median  basilic  vein,  which  unites  with  the  common 
ulnar  to  form  the  basilic.  The  artery  here  lies  in  a  triangle 
bounded  internally  by  the  pronator  radii  teres,  externally  by 
the  supinator  longus  and  above  by  a  line  drawn  from  one 
condyle  of  the  humerus  to  the  other. 

Branches. 

Superior  Profunda  Inferior  Profunda 

Anastomotica  Magna. 

The  snf)cri(}r  -profunda  arises  from  the  upper  part  of  the 
brachial,  and  passes  downward  and  outward.  After  piercing 
the  intermuscular  septum,  it  winds  around  the  humerus  in  the 
musculo-spiral  groove,  accompanying  the  nerve  of  that  name; 
and  on  reaching  the  outer  border  of  the  humerus,  divides  into 
two  branches.     One  of  these  pierces  the  external  inter-muscu- 


314  DESCRIPTIVE  ANATOMY. 

lar  septum;  and  continues  downward  in  the  interval  between 
the  supinator  long'us  and  the  brachialis  anticus  to  anastomose 
with  the  recurrent  branch  from  the  radial,  while  the  other 
branch  continues  its  course  behind  the  external  inter-muscu- 
lar septum  to  anastomose  with  the  posterior  interosseous 
recurrent  and  also  with  the  anastomotica  mag^na,  the  inferior 
profunda  and  the  posterior  ulna  recurrent. 

The  inferior  profunda  ds'x'&Q-'i  a  little  above  the  middle  of  the 
vessel,  just  below  the  superior.  It  immediately  seeks  the 
ulna  nerve;  and  with  that  nerve  pierces  the.  internal  inter- 
muscular septum  to  pass  to  the  inner  back  part  of  the  elbow 
joint,  w^here  it  anastomoses  with  the  anastomotica  mag-na  and 
the  posterior  ulna  recurrent. 

The  anastomotica  inag-)ia  arises  near  the  termination  of  the 
brachial,  about  two  inches  above  the  elbow  joint.  It  runs  di- 
rectly inward  to  the  inner  aspect  of  the  arm,  anastomoses  with 
the  anterior  ulna  recurrent,  pierces  the  inter-muscular  septum, 
passes  outward  beneath  the  triceps,  or  sometimes  through  the 
fibres  of  that  muscle,  anastomoses  with  the  inferior  profunda 
and  the  posterior  ulna  recurrent  on  the  inner  aspect  of  the 
elbow  joint,  with  the  posterior  branch  of  the  superior  pro- 
funda upon  the  outer  aspect  of  the  elbow  joint,  and  with  the 
posterior  interosseous  recurrent  and  with  the  anterior  ulna 
recurrent.  Thus  the  only  branch  forming-  the  vascular  circle 
around  the  elbow  joint  with  which  the  anastomotica  mag"na 
does  not  anastomose  is  the  radial  recurrent. 

The  anastomotica  mag-na  is  thus  the  chief  artery  in  completing- 
the  chain  around  the  elbow.  Passing-  inward  it  receives  a 
communication  from  the  anterior  ulnar  recurrent:  then  from 
the  inferior  profunda  and  posterior  ulna  recurrent;  then,  on 
the  outer  side  of  the  arm,  from  the  posterior  branch  of  the 
superior  profunda,  whose  anterior  branch  has  already  inoscu- 
lated with  the  radial  recurrent. 

The  Arteries  of  the  Forearm. 

The  arteries  of  the  forearm  are  the  radial  and  ulnar  and  their 
branches. 


THE  VASCULAR  SYSTEM.  315 

Radial  Artery  on  the  Forearm. 

The  radial  artery,  one  of  the  two  terminal  branches  of  the 
brachial,  begins  where  that  arterj  divides  about  half  an  inch 
below  the  middle  of  the  front  of  the  elbow,  and  passes  down- 
ward with  such  an  inclination  outward  as  to  bring-  it  to  the 
outer  side  of  the  front  of  the  wrist  joint,  where  it  lies  on  the 
front  of  the  styloid  -process  of  the  radius,  terminating  as  the 
radial  artery  of  the  forearm  by  becoming  the  radial  artery  of 
the  zL'rist. 

Relations.  To  the  outer  side  it  has  throughout  its  course  the 
supinator  longus,  whose  belly  overlaps  it.  With  this  excep- 
tion the  artery  is  superficial.  To  its  inner  side  is  first  the 
pronator  radii  teres,  and,  when  that  muscle  is  inserted,  its 
place  is  taken  by  the  flexor  carpi  radialis  which  remains  to  the 
inner  side. 

It  is  accompanied  by  satellite  veins,  one  on  either  side,  and 
in  the  middle  third  of  its  course  has  the  radial  nerve  to  its 
outer  side.  The  nerve  in  the  upper  third  is  too  far  away  to  be 
considered  a  relation,  while  in  the  lower  third  it  passes  be- 
neath the  tendon  of  the  supinator  longus  and  disappears  on  the 
back  of  the  forearm. 

Behind  it  lie  the  tendons  of  the  biceps,  the  supinator  brevis, 
the  insertion  of  the  pronator  radii  teres,  a  part  of  the  origin  of 
the  flexor  sublimis  digitorum,  a  portion  of  the  flexor  longus 
pollicis,  and  the  pronator  quadratus.  Below  these  is  the  front 
of  the  shaft  of  the  radius. 

Ulnar  Artery  on  the  Forearm. 

The  zilnar  artery,  the  larger  of  the  two  terminal  branches  of 
the  brachial,  begins  where  that  artery  terminates  about  half 
an  inch  below  the  middle  of  the  front  of  the  elbow,  by  dividing 
into  itself  and  the  radial,  and  passes  first  downward  and  inward 
for  the  upper  third  of  its  course,  to  the  inner  side  of  the  front 
of  the  forearm  and  then  turns  vertically  downward  to  reach  the 
inner  side  of  the  front  of  the  wrist,  where  it  terminates  as  the 
ulnar  artery  of  the  forearm  by  becoming  the  ulnar  artery  of 
the  hand. 


316  DESCRIPTIVE  ANATOMY. 

Relations.  In  the  first  part  of  its  course,  while  it  is  passing" 
downward  and  inward,  it  lies  beneath  four  muscles,  viz:  prona- 
tor radii  teres,  flexor  carpi  radialis,  palmaris  long-usand  flexor 
sublimis  dig-itorum — all  the  muscles  of  the  superficial  group 
except  the  flexor  carpi  ulnaris.  When  it  emerges  from  beneath 
these  muscles  it  descends  with  the  tendon  of  the  flexor  carpi 
ulnaris  to  its  inner  and  of  the  flexor  sublimis  digitorum  to  its 
outer  side.  In  its  upper  portion  it  lies  on  the  brachialis  anti- 
cus  and  in  its  lower  portion  on  the  flexor  profundus  digitorum. 
It  is  accompanied  by  satellite  veins,  one  to  either  side,  and 
for  its  lower  two-thirds  has  to  its  inner  side  the  ulnar  nerve. 
In  its  upper  part  it  is  crossed  by  the  median  nerve  which  is  also 
an  external  relation  for  about  an  inch. 

Ulnar  Artery  in  the  Hand. 

When  the  ulnar  artery  reaches  the  wrist  it  continues  its 
course  into  the  palm  of  the  hand,  lying  close  to  and  on  the  outer 
side  of  the  pisiform  bone  and  on  the  anterior  annular  ligament. 
After  passing  down  a  short  distance  into  the  palm,  it  turns 
outward  and  runs  across  the  palm  of  the  hand  to  its  outer  side, 
being-  covered  only  by  the  skin  and  fascia  and  lying  on  the 
flexor  tendons  and  on  the  origin  of  the  muscles  of  the  little 
finger,  and  on  the  divisions  of  the  median  and  ulna  nerves. 
Its  course  across  the  palm  is  known  as  the  superficial  falmar 
arch  (arcus  sublimis)  and  though  its  direction  is  not  transverse, 
it  is  more  or  less  clearly  defined  by  a  transverse  line  across 
the  palm  drawn  from  the  bottom  of  the  interval  between  the 
thumb  and  index  fi^nger.  The  ulnar  nerve  continues  its  rela- 
tion to  the  artery  in  the  hand,  lying  to  its  inner  side. 

Branches. 

Anterior  Ulnar  Recurrent  Interosseous 

Posterior  Tlnar  Recurrent  Muscular 

The  anterior  ulnar  recurrent  arises  from  the  ulnar  just 
below  its  origin  and  passes  upward  to  the  front  of  the  inner 
side  of  the  elbow,  where  it  inosculates  with  the  anastomotica 
magna.  The  -posterior  ulnar  recurrent  rises  just  below  the 
preceding  and   passes  upward  and  backward  to  the  internal 


THE  VASCULAR  SYSTEM.  317 

condyle.  It  passes  to  the  interval  between  the  olecranon  and 
internal  condyle  and  communicates  with  the  anastomotica 
mag-na  and  the  inferior  profunda. 

The  interosseous  is  a  lar^-e  trunk  which  arises  from  the 
ulnar  just  below  the  elbow  and  quickly  forks  into  an  anterior 
and  posterior  interosseous. 

1st.  The  anterior  interosseous  descends  on  the  front  of  the 
interosseous  membrane,  between  the  flexor  profundus  digito- 
rum  and  flexor  long-us  poUicis  muscles,  to  the  pronator  qua- 
dratus,  passing-  beneath  which  it  perforates  the  interosseous 
membrane  and  appears  on  the  back  of  the  forearm  to  inoscu- 
late with  the  posterior  interosseous  artery.  It  supplies  the 
muscles  in  its  route  and  gives  off  a  companion  branch  to  the 
median  nerve.  It  communicates  with  the  posterior  carpal 
arch  and  the  posterior  interosseous. 

2nd.  The  posterior  interosseous,  as  soon  as  it  is  produced, 
passes  between  the  bones  above  the  interosseous  membrane, 
to  reach  the  back  of  the  forearm  and  descend  on  the  back  of 
the  forearm,  between  the  superficial  and  deep  layer  of  muscles, 
to  the  wrist.  Just  as  it  reaches  the  back  of  the  forearm  it 
gives  off  a  large  branch,  called  the  posterior  interosseous  re- 
current, which  ascends  to  the  back  of  the  elbow  and  commu- 
nicates with  the  anastomotica  magna. 

The  posterior  interosseous  artery  is  distributed  to  adjacent 
muscles. 

The  muscular  branches  of  the  ulnar  artery  are  numerous 
twigs  to  muscles  in  its  course. 

Branches  at  the  Wrist. 

Anterior  Carpal  Posterior  Carpal 

The  (Ulterior  carpal  is  a  branch  which  passes  outward  on 
the  front  of  the  wrist  to  inosculate  with  the  anterior  carpal 
of  the  radial.  From  this  arch  branches  pass  to  the  carpal  ar- 
ticulations. 

The  posterior  carpal  "^di^^ts  backward  and  then  runs  outward 
on  theback  of  the  wrist  to  anastomose  with  the  posterior  carpal 
of  the  radial.  From  this  arch  are  given  off  branches  which 
supply  the  ulnar  side  of  the  back  of  the  little  finger  and  inter- 


318  DESCRIPTIVE  ANATOMY. 

osseous  branches  to  the  next  two  spaces.     These  branches  re- 
ceive the  posterior  and  anterior  perforating'  arteries. 

These  branches  are  very  small  and  the  anterior  is  frequently 
absent. 

Branches  in  the  Hand. 

Communicating  Dig-ital 

The  communicating-  branch  dips  between  the  abductor  mi- 
nimi digiti  and  flexor  brevis  minimi  digiti  to  join  the  termi- 
nation of  the  radial,  completing-  the  deep  palmar  arch. 

The  thumb  and  each  of  the  fingers  have  two  palmar  arteries, 
one  on  either  side,  and  two  dorsal,  similarly  arranged,  running 
from  base  to  tip,  called  respectively  ^«/?;^«r  and  dorsal  collateral 
dig-ital  arteries.  The  digital  arteries  now  under  consideration 
are  four  in  number,  from  the  superficial  palmar  arch.  The 
first  is  a  small  branch  which  supplies  the  inner  side  of  the  lit- 
tle finger  ;  the  second  supplies  adjacent  sides  of  the  little  and 
ring  fingers,  splitting  at  the  cleft  between  the  two  ;  the  third 
does  the  same  for  adjacent  sides  of  the  middle  and  ring  fingers 
and  the  fourth  for  adjacent  sides  of  the  middle  and  index 
fingers. 

These  branches  run  along  either  side  of  the  fingers  until 
they  reach  the  tip  ;  where,  after  giving  off  small  branches 
which  run  beneath  the  nail  and  communicate  with  the  dorsal 
arteries  they  inosculate  with  one  another,  completing  the  loop 
between  the  palmar  arch  and  the  digital  arteries. 

Radial  Artery  of  Wrist  and  Hand. 

When  the  radial  artery  reaches  the  wrist  it  turns  outward, 
backward  and  downward  beneath  the  extensor  tendons  of  the 
thumb,  viz:  the  extensor  ossis  metacarpi  pollicis,  extensor 
primiand  extensor  secondiinternodiipollicis,in  the  order  named, 
and  passing  through  what  is  known  as  the  snuff  box — the 
sunken  interval  between  the  extensor  ossis  metacarpi  pollicis 
and  extensor  primi  internodii  pollicis  on  one  side  and  the 
extensor  secundi  internodii  pollicis  on  the  other — reaches  the 
back  of  the  hand  where  its  appearance  is  only  momentary, 
for  it  immediately  dips  into  the  palm  of  the  hand  by  passing 
between  the  two  heads  of  the  first  dorsal  interosseous  muscle, 


THE  VASCULAR  SYSTEM.  319 

and  passinof  across  the  palm  of  the  hand  from  the  outer  to  the 
inner  side,  terminates  by  anastomosing-  with  the  communicat- 
ing:;- branch  from  the  superficial  palmar  arch.  The  position  of 
the  radial  in  the  palm  is  deep,  lying-  on  the  bases  of  the  meta- 
carpal bones  and  beneath  the  flexor  tendons  which  separate  it 
from  the  superficial  palmar  arch.  It  is  called  the  deep  palmar 
arch  and  is  situated  about  half  an  inch  nearer  the  wrist  than 
the  superficial  arch. 

Branches  of  the  Forearm. 

Recurrent  Radial  Muscular 

The  recurrent  radial  arises  from  the  radial  just  below  the 
elbow  and  passes  upward  and  outward  to  the  outer  side  of  the 
front  of  tne  joint,  where  it  lies  in  the  space  between  the  supina- 
tor long-US  and  the  brachialis  anticus.  It  here  inosculates  with 
the  anterior  branch  of  the  superior  profunda. 

The  muscular  branches  are  numerous  twig-s  to  muscles  in 
the  course  of  the  artery. 

Branches  at  the  Wrist. 

Superficialis  Vols  Dorsalis  Pollicis 

Anterior  Carpal  Metacarpea 

Posterior  Carpal  Dorsalis  Indicis 

Princeps  Pollicis 

The  su-perjicialis  voice  leaves  the  radial  just  as  it  turns  out- 
ward and  passes  to  the  muscles  of  the  thenar  g-roup,  usually 
perforating-  the  abductor  pollicis.  Sometimes  it  anastomoses 
with  the  termination  of  the  ulna,  forming-  the  superficial  arch. 

The  anterior  carfal  branch  passes  inward  on  the  front  of 
the  joint  to  form  the  anterior  carpal  arch  by  uniting-  with  the 
anterior  carpal  of  the  ulnar  artery. 

The  -posterior  carpal  passes  inward  across  the  back  of  the 
wrist  to  inosculate  with  the  posterior  carpal  of  the  ulnar  and 
form  the  posterior  carpal  arch.  From  the  posterior  carpal 
arch  there  pass  down  on  the  dorsal  interosseous  muscle  two 
branches  called  posterior  interosseous  besides  another  which 
runs  along-  the  dorsal  aspect  of  the  ulnar  border  of  the 
hand    to    supply    the    ulnar    side    of   the   dorsal    aspect    of 


320  DESCRIPTIVE  ANATOMY. 

the  little  fing^er.  The  posterior  interosseous  pass  down- 
ward to  divide  the  one  at  the  cleft  between  the  little  and 
ring-  fingers  to  form  dorsal  collateral  dig-ital  branches  for  the 
adjacent  sides  of  those  fino-ers,  while  the  other  performs  a 
similar  duty  for  the  adjacent  sides  of  the  ring-  and  middle 
fingers. 

Just  as  the  radial  is  passing-  the  root  of  the  thumb  it  gives 
off  two  small  branches  which  course  along-  the  sides  of  the 
dorsal  aspect  of  the  thumb.     They  are  called  dorsales  -pollicis. 

The  nietacarpea  is  a  branch  which  descends  on  the  second 
dorsal  interosseous  muscle  to  the  cleft  between  the  middle 
and  index  fing-ers  and  there  divides  to  form  dorsal  collateral 
digital  branches  for  those  fingfers. 

The  dor  salts  indicis  is  a  small  branch  which  passes  forward 
to  form  the  dorsal  collateral  digital  branch  for  the  outer  side 
of  the  index  fing-ers. 

Princeps  Pollicis. 

ThQ  ;p7-mceps  pollicis  arises  just  as  the  radial  dips  into  the 
palm  of  the  hand  and  passes  forward  and  outward  to  divide  and 
form  collateral  dig-ital  arteries  for  the  palmar  aspect  of  the 
thumb. 

Branches  of  the  Deep  Palmar  Arch. 

Radialis  Indicis  Anterior  Interosseous 

Perforating- 

1st.  The  radialis  indicis,  coming-  off  close  to  the  princeps 
pollicis,  runs  along-  the  radial  border  of  the  index  fing-er  to  ifs 
extremity  and  there  anastomoses  with  the  collateral  dig-ital 
artery  of  the  superficial  palmar  arch.  It  also  anastomoses 
with  the  princeps  pollicis  and  g^ives  a  communicating-  branch 
to  the  superficial  palmar  arch  thus  completing-  the  arch,  thoug-h 
sometimes  the  superficial  arch  is  completed  by  anastomosing- 
with  the  superficialis  volae. 

The  anterior  interosseous  are  three  or  four  small  branches 
which  pass  forward  on  the  front  of  the  interosseous  muscles 
to  unite  with  the  dig-ital  branches  of  the  superficial  arch. 

Besides  these  the  deep  arch  g-ives  off  two  sets  of  unimpor- 
tant branches  called  perforating  and  recurrent. 


THE  VASCULAR  SYSTEM.  321 

The  -perforating  arteries  are  three  in  number,  passing-  back- 
ward between  the  heads  of  the  last  three  dorsal  interosseus 
muscles  they  inosculate  with  the  dorsal   interosseous  arteries. 

The  Aorta. 

The  Aorta  commences  at  the  base  of  the  arterial  ventricle, 
and  terminates  by  dividing-  into  the  common  iliac  arteries  on 
the  front  of  the  bod}"  of  the  fourth  lumbar  vertebra  slig-htly 
to  the  left  of  the  raid-line.  It  lies  first  in  the  thoracic,  then  in 
the  abdominal  cavity.  Its  direction  is  first  upward,  forward, 
and  to  the  rig-ht;  then  backward,  and  to  the  left;  and  finally  it 
turns  downward  until  it  reaches  its  point  of  bifurcation.  It 
is  divided  for  description  into  the  Ascending-  Aorta,  the  Trans- 
verse Aorta,  and  the  Descending  Aorta,  the  latter  being-  sub- 
divided into  the  Thoracic  and  Abdomiiial  portion  of  the 
descending  aorta.  The  old  sub-divisions  of  ascending,  trans- 
verse, and  descending  portions  of  the  arch  have  here  been 
abandoned. 

The  Ascending  Aorta. 

The  Ascending-  Aorta  (formerly  called  the  Ascending- Por- 
tion of  the  Arch  of  the  Aorta)  begins  at  the  base  of  the  arterial 
ventricle,  at  a  point  behind  the  left  edg-e  of  the  sternum,  oppo- 
site the  third  intercostal  space,  on  a  plane  posterior  to  the 
pulmonary  artery  and  anterior  to  the  left  auriculo-ventricular 
opening.  It  is  about  two  inches  in  length,  is  directed  upward, 
forward,  and  to  the  right,  presenting-  a  slig-ht  curve,  whose 
convexity  is  to  the  rig-ht.  Behind  the  upper  border  of  the  sec- 
ond costal  cartilage  of  the  rig-ht  side  it  terminates  by  becoming- 
the  transverse  aorta.  Just  above  its  orig-in  it  is  somewhat 
triangular  on  cross-section  when  distended,  and  presents  three 
bulg-ing-  prominences,  which  correspond  to  the  sinuses  of 
Valsalva.  It  lies  in  the  fibrous  pericardium,  about  one-fourth 
of  an  inch  behind  the  sternum;  and  is  contained  in  the  same 
fold  of  serous  pericardium  as  the  pulmonary  artery. 

Relations.  On  its  anterior  aspect,  at  its  origin,  lies  the  pul- 
monary artery  ;  but  this  vessel  quickly  winds  to  the  left  of 
the  aorta,  owing  partly  to  the   inclination  of  the   aorta  to  the 

Des  Anat— 21 


322  DESCRIPTIVE  ANATOMY. 

right,  and  partly  to  the  oblique  course  of  the  pulmonary  artery. 
Above  the  pulmonary , the  aorta  is  separated  from  the  sternum  by 
the  pericardium,  some  loose  connective  tissue,  and  the  remains 
of  the  thymus  g-land,  should  any  exist.  At  its  oriofin  it  is  over- 
lapped in  front  by  the  rig-ht  auricular  appendix  ;  behind  it 
lies  the  right  pulmonary  artery,  and  other  structures  which 
enter  into  the  formation  of  the  root  of  the  right  lung,  and  the 
left  auricle  of  the  heart.  To  its  right  at  its  base  is  the  right 
auricle  ;  and  above  this  the  superior  vena  cava.  To  the  left, 
as  already  seen,  is  the  pulmonary  artery. 

The  Transverse  Aorta. 

The  Transverse  Aorta  begins  by  being  a  continuation  of 
the  ascending  aorta  opposite  the  upper  border  of  the  second 
right  costal  cartilage  ;  and  with  a  gentle  curve  in  its  course, 
passes  from  right  to  left  from  before  backward,  and  slightly 
from  above  downward,  to  terminate  at  the  left  side  and  lower 
'border  of  the  fourth  dorsal  vertebra,  by  becoming-  the  descend- 
ing aorta.  The  top  of  this  arch  is  about  an  inch  below  the 
top  of  the  sternum  ;  and  from  it  arise  three  large  branches  : 
the  Arteria  hinominata,  the  left  Common  Carotid  and  the 
Left  Sub-clavian. 

Relations.  In  front  it  is  overlapped  very  slightly  by  the  right 
pleura,  and  to  a  much  greater  extent  by  the  left  pleura  and 
lung,  though  the  two  pluras  do  not  come  in  contact.  It  is 
crossed  in  the  order  from  right  to  left  by  the  left  phrenic,  the 
cardiac  branches  of  the  pneumogastric,  and  the  left  pneumogas- 
tric  nerves.  The  left  superior  intercostal  vein  also  crosses 
the  front  of  the  transverse  aorta.  Behind,  it  rests  upon  the 
trachea,  behind  that  is  the  oesophagus,  and  in  the  interval  be- 
tween the  two  the  thoracic  duct  and  the  left  recurrent  laryn- 
geal nerve.  Above,  it  is  in  relation  with  its  three  branches 
before  mentioned,  from  right  to  left,  and  from  before  back- 
ward, the  arteria  innomiuata,  left  common  carotid,  and  left  sub- 
clavian ;  while  above  and  towards  its  front  aspect  is  found  the 
great  transverse  vein  of  the  neck,  or  the  left  innominate  vein. 
Below  it  are  the  bifurcation  of  the  pulmonary  artery,  the  left 
bronchus,  and  the  left  recurrent  laryngeal  nerve,  while  it  is 


THE  VASCULAR  SYSTEM.  323 

connected  by  means  of  the  ductus  arteriosus  with  the  pulmo- 
nar}"  artery.  The  portion  formerly  described  as  "the  descend- 
ing" portion  of  the  arch  of  the  aorta"  will  be  considered  with 
the  thoracic  aorta. 

Branches  of  the  Ascending  Aorta. 

Coronary  Arteries. 

The  right  and  left  coronary  branches  2x\'&^  from  the  ascend- 
ing- aorta.  These  branches  arise  from  the  corresponding- 
sinuses  of  Valsalva,  the  right  arising-  from  the  right  anterior 
sinus,  and  the  left  from  the  left  anterior  sinus.  They  descend 
into  the  anterior  and  posterior  inter-ventricular  furrows,  and 
meet  at  the  apex  of  the  heart.  Here  they  inosculate  with  one 
another,  while  each  sends  off  a  branch  to  supply  the  auriculo- 
ventricular  grooves,  anastomosing  with  one  another,  and  form- 
ing- two  vascular  circles  at  rig-ht  ang-les  with  one  another, 
which  completely  surround  the  heart. 

Branches  of  the  Transverse  Aorta. 

Arteria  lunominata  Left  Common  Carotid 

Left  Subclavian 

The  branches  which  spring-  from  the  transverse  aorta  are 
three  in  number,  and  bear  a  definite  relation  to  one  another; 
that  is,  the  first,  the  Arteria  Innominata,  arises  near  the  com- 
mencement of  the  transverse  aorta;  the  left  C<^mmon  Carotid 
at  the  middle  of  the  transverse  aorta;  and  the  left  Subclavian 
near  the  termination  of  the  transverse  aorta. 

Arteria  Innominata. 

The  arteria  i)i)ionii}iata  is  the  first  and  doubly  the  larg-est 
branch  of  the  aorta.  It  arises  from  the  beg-inning-  of  the  trans- 
verse aorta,  passes  upward  and  to  the  rig-ht  for  a  little  less 
than  two  inches  to  terminate  behind  the  upper  border  of  the 
right  sterno-clavicular  articulation  h^  dividing-  into  the  Right 
Common  Carotid  and  Rig-ht  Subclavian  arteries.  In  other 
words,  in  it  are  blended  the  rig-ht  common  carotid  and  right 
subclavian  vessels. 

Relations.  In  front  is  the  sternum,  from  which  it  is  separa- 
ted by  some  loose  connective  tissue,  by  the  prolong-ation  of  the 


324  DESCRIPTIVE  ANATOMY. 

fibres  of  origin  of  the  sterno-hyoid  and  sterno-thyroid  muscles, 
and  by  the  remains  of  the  thymus  g-land,  should  there  be  any. 
Across  the  front  of  it,  just  at  its  orig-in,  passes  the  left  innomi- 
nate vein,  or  g-reat  transverse  vein  of  the  neck,  and  the  right 
inferior  thyroid  vein.  Behind,  at  its  commencement,  it  rests 
upon  the  trachea  ;  but  the  obliquity  of  the  artery  soon  carries 
it  to  the  right  of  the  trachea,  which  then  becomes  a  left  or 
internal  relation  to  the  arteria  innominata.  On  the  right  side  is 
the  right  innominate  vein,  the  right  pleura,  and  the  right  pneu- 
mogastric  nerve,  which  is  a  rather  distant  relation.  On  the 
left  at  its  commencement  is  the  left  common  carotid  artery, 
which  lies  to  the  left  and  on  a  plane  slightly  posterior,  sepa- 
rated from  the  arteria  innominata  by  a  triangular  interval  in 
which  the  trachea  may  be  seen.  Higher  up  is  the  trachea. 
It  usually  produces  no  branches  except  its  terminal  branches. 
The  remains  of  the  thymus,  and  the  left  inferior  thyroid  vein 
are  also  relations  on  its  left. 

Left  Common  Carotid. 

The  left  common  carotid,  the  second  branch  arising  from 
the  transverse  aorta,  occupies  a  position  midway  between  the 
innominate  and  left  subclavian  arteries. 

Relations .  Its  relations  in  the  thorax  are  somewhat  similar 
to  those  of  the  arteria  innominata,  but  not  identical  with  them. 
After  passing  above  th>e  left  sterno-clavicular  articulation,  its 
relations  become  identical  with  those  of  the  right  common 
carotid,  and  a  description  of  one  answers  for  the  other.  It 
springs  from  the  highest  portion  of  the  transverse  aorta,  lying 
with  the  innominate  to  its  right  and  on  a  plane  slightly  ante- 
rior, the  left  subclavian  to  its  left  and  on  a  plane  slightly  pos- 
terior. It  is  separated  from  the  sternum  by  the  origin  of  the 
sterno-thyroid  and  sterno-hyoid  muscles  of  the  left  side,  some 
loose  connective  tissue,  and  the  remains  of  the  thymus  gland  ; 
and  is  crossed  in  front  by  the  great  transverse  vein,  though  at  a 
higher  level  thanthatat  which  the  same  vein  crosses  the  innom- 
inate artery.  It  is  overlapped  in  front  by  the  left  lung  and 
pleura.  Behind  it,  at  its  origin,  lies  the  trachea,  which  is  be- 
hind and  slightly  to  its  inner  side.     Crossing  obliquely  behind 


THE  VASCULAR  SYSTEM.  325 

is  the  left  recurrent  lar^^ng-eal  nerve  while  behind  and  to  its 
outer  side  is  seen  the  thoracic  duct.  As  it  ascends,  the  tra- 
chea becomes  an  internal  relation,  and  the  oesophag-us  a  pos- 
tero-internal  relation,  the  recurrent  laryng-eal  nerve  lying-  in 
the  g-roove  between  these  two  structures.  To  its  inner  side 
at  its  commencement  is  the  innominate  artery;  and  above  this, 
and  internal  and  posterior  to  it,  the  trachea.  To  its  inner 
side  is  also  the  inferior  thyroid  vein.  To  its  outer  side  is  the 
left  subclavian,  which  is  external  and  slig^htly  posterior;  while 
in  the  interval  between  the  subclavian  and  the  carotid  is  seen 
the  pneumog^astric  nerve,  an  antero-external  relation  of  the 
carotid. 

The  Left  Subclavian. 

The  left  sKbclavicnid.ri^,^'^  from  the  termination  of  the  trans- 
verse aorta.  It  passes  upward  and  to  the  left;  and  its  first  or 
thoracic  portion  terminates  at  the  inner  edge  of  the  scalenus 
anticus  muscle  by  becoming  the  second  portion  of  the  artery. 
From  this  point  to  its  termination,  the  left  subclavian  is  iden- 
tical with  the  right. 

Relations.  The  left  subclavian  is  almost  enveloped  by  the 
left  pleura,  which  covers  it  in  front,  to  the  outer  side,  and 
behind.  It  has  the  left  common  carotid  lying  internal  to  it 
and  slig-htly  in  front  of  it,  while  more  superficially^  are  the 
origins  of  the  sterno-hyoid  and  sterno-thyroid  muscles,  and 
the  remains  of  the  thymus  gland,  should  there  be  any.  Near 
its  origin,  but  hig-her  than  at  the  point  of  crossing-  of  the  left 
common  carotid,  is  found  theg^reat  transverse  vein  of  the  neck, 
while  near  the  termination  of  the  first  portion  the  internal 
jug-ular  and  the  subclavian  veins  of  the  left  side  unite  to  form 
the  innominate  on  the  front  of  the  subclavian  artery.  The 
left  vertebral  vein  is  also  an  anterior  relation.  The  phrenic 
nerve  crosses  it  near  the  scalenus  anticus  muscle,  and  then 
passes  downward,  parallel  to  the  pneumog-astric,  but  external 
to,  and  in  front  of,  that  nerve.  The  pneumog*astric  itself  lies 
in  the  interval  between  the  subclavian  and  the  left  common 
carotid  on  a  plain  anterior  to  both,  but  internal  to  the  subcla- 
vian, while  external  to  the  carotid.  Below  it,  as  well  as  to  its 
outer  side,   are  the   pleura  and  the   left  lung".     The  trachea, 


326  DESCRIPTIVE  ANATOMY. 

oesophagus,  and  recurrent  lar3^ng-eal  nerve  migflit  be  considered 
distant  internal  relations.  The  relation  of  the  thoracic  duct 
should  be  carefully  noted.  It  ascends  nearly  opposite  the 
interval  between  the  left  common  carotid  and  the  subclavian, 
passes  above  the  point  at  which  the  subclavian  arches  outward 
toward  the  scalenus  anticus  muscle,  then  turns  to  the  front 
of  the  arterv  to  empty  into  the  junction  of  the  internal  jug-ular 
and  subclavian  veins,  so  that  its  relationship  to  the  artery  is  a 
three-fold  one:  being-  first  behind  it,  then  above  it,  then  in  front 
of  it,  at  its  termination. 

The  Descending  Aorta. 

The  descending-  aorta  commences  by  being  a  continuation  of 
the  transverse  aorta  at  the  left  side  and  lower  border  of  the 
body  of  the  fourth  dorsal  vertebra,  and  terminates  opposite 
the  bod}^  of  the  fourth  lumbar  vertebra  by  dividing-  into  the 
two  common  iliacs.  It  consists  of  the  Thoracic  and  Abdomi- 
nal Portions. 

The  Thoracic  Aorta. 

The  thoracic  -portion  of  the  descending-  aorta,  commencing 
at  the  fourth  dorsal  vertebra,  terminates  opposite  the  body  of 
the  twelfth  dorsal,  slightly  to  the  left  of  the  mid-line,  by  h^- 
coming  the  addoniif ml  ao)'ta.  The  course  of  the  thoracic  aorta 
is  downward,  with  a  slight  inclination  to  the  right,  so  that 
from  lying  first  upon  the  lateral  aspect  of  the  body  of  the  fifth 
dorsal,  it  changes  its  relative  position  to  the  bodies  of  the  ver- 
tebrae to  such  a  degree  that  at  its  point  of  termination  it  is 
on  the  front  of  the  bodies,  and  but  slightly  to  the  left  of  the 
mid-line.  It  presents  a  curve  in  its  course  slightly  concave  in 
front  to  correspond  with  the  dorsal  curvature  of  the  spinal 
column  upon  which  it  rests. 

Relations .  This  vessel  is  covered  throug'hout  its  course  by 
the  pleura;  and  lies  with  other  important  structures  in  the  pos- 
terior mediastinum.  In  front,  opposite  the  body  of  the  fifth 
dorsal  vertebra,  is  the  root  of  the  left  lung,  consisting  mainly 
of  the  pulmonary  artery,  the  pulmonary  veins,  the  left  bron- 
chus, lymphatics,  nerves,  and  small  blood  vessels.  Below  this 
it  lies  behind  the  pericardium;  and  is  completely  covered  over 


THE  VASCULAR  SYSTEM.  327 

by  the  left  pleura  and  lung-.  It  bears  an  important  relation  to 
the  (jesophag-us,  thoracic  duct,  and  pneumogfastric  nerves.  The 
two  pneumogastric  nerves  course  downward,  one  upon  the 
front  and  the  other  upon  the  back  of  the  oesophagus,  and  hence 
bear  the  same  relation  to  the  aorta  that  this  structure  does. 
Owing-  to  the  changes  in  the  direction  of  the  oesophagus  as  well 
as  to  the  obliquity  of  the  aorta,  the  oesophagus  above  lies  to  the 
right  of  the  descending  aorta.  About  the  middle  of  the  course 
of  the  artery  it  is  directly  in  front  of  it,  while  opposite  the 
tenth  dorsal  vertebra,  where  the  (jesophagus  terminates,  it  is 
still  further  in  front  and  to  the  left  of  the  aorta.  The  thoracic 
duct  is  continuously  behind  and  slightly  to  the  right  of  the 
aorta,  lying  usually  in  the  interval  between  the  aorta  and  the 
great  azygos  vein.  To  the  right  of  the  aorta  is  the  great  azy- 
gos  vein,  opening  into  which  opposite  the  sixth  dorsal  vertebra 
is  the  left  azygos,  which  crosses  behind  the  aorta.  The  extent 
to  which  the  aorta  is  covered  by  the  pleura  decreases  as  it  de- 
scends. In  the  upper  portion  of  its  course,  all  of  the  vessel 
except  a  small  part  of  its  right  side,  which  rests  upon  the 
bodies  of  the  vertebra?,  is  enveloped  by  the  pleura,  while  near 
its  termination  the  pleura  covers  only  its  outer  aspect. 

Branches. 

Bronchial  Intercostal 

Mediastinal  Pericardiac 

(Esophageal 

The  hrcuiclies  of  the  th')racic  aorta  are  small,  although  there 
are  a  large  number  of  them. 

The  bronchial  arteries,  usually  three  to  the  left  and  one  to 
the  right  lung,  course  along  the  bronchi  to  the  lungs,  and  ram- 
ify with  the  bronchial  tubes.  These  vessels,  it  should  be 
understood,  have  no  connection  with  the  pulmonary  artery  ; 
but  simply  furnish  a  nutrient  supply  for  the  lung  tissue  it- 
self. Their  method  of  distribution  belongs  to  the  domain  of 
histology. 

The  (vsophafccal  are  a  number  of  small  twigs,  four  or  five, 
which   are  successively   furnished  to  the  (esophagus  as  that 


328  DESCRIPTIVE  ANATOMY. 

tube  comes  into  relationship  with  the  thoracic  aorta,  and  which 
communicate  with  one  another  and  with  other  oesophageal 
arteries. 

The  mediastinal  and  -pericardiac  are  small  twigs  furnished 
to  the  posterior  mediastinum  and  to  the  pericardium  respec- 
tively. 

The  intercostal,  the  largest  and  most  numerous  of  the  branch- 
es, are  ten  pairs,  which  rise  from  both  sides  of  the  thoracic 
aorta,  and  run  out  into  the  intercostal  spaces,  the  upper  space 
being-  supplied  by  the  superior  intercostal  of  the  subclavian, 
while  the  space  below  the  last  rib,  or  sub-costal  space,  is  sup- 
plied by  one  of  the  terminal  branches  of  the  internal  mammar3^ 
The  right  intercostal  arteries  are,  of  course,  longer  than  the 
left  from  having  to  cross  the  vertebral  column.  Kach  inter- 
costal artery  passes  outward  in  its  corresponding  space  to  run 
along  the  lower  border  of  the  rib  above  in  the  groove  which  is 
formed  for  lodging  the  artery  and  the  nerve;  and  after  going 
some  distance,  gives  off  a  branch,  which  descends  to  course 
along  the  upper  border  of  the  rib  below.  The  arteries  of  the 
right  side  pass  behind  the  venaazygos  major  and  thoracic  duct. 
Further  out  they  pass  behind  the  sympathetic  system;  and  lie 
first  upon  the  external  intercostal  muscle,  and  then,  at  the  an- 
gle of  the  rib,  between  the  two  intercostal  muscles.  They 
continue  their  course  to  finally  inosculate  with  the  intercostal 
branches  from  the  internal  mammary  for  the  upper  spaces,  and 
those  from  the  musculo-phrenic  for  the  lower  spaces.  Before 
terminating  each  intercostal  gives  off  a  dorsal  branch,  whose 
distribution  corresponds  to  the  dorsal  nerves;  that  is,  it  divides 
into  a  muscular  and  a  spinal  branch,  the  spinal  to  enter  the  spi- 
nal canal,  and  the  muscular  to  be  distributed  to  the  deep  muscles 
of  the  back. 

The  Abdominal  Aorta. 

The  abdominal  aorta  commences  on  the  body  of  the  twelfth 
dorsal  vertebra,  slightly  to  the  left  of  the  mid-line,  being  a 
continuation  of  the  thoracic  aorta.  It  passes  behind  the  dia- 
phragm, through  the  aortic  opening,  and  curves  backward  and 
and  to  the  left,  the  convexity  being  to  the  left.  About  the 
middle  of  its  course  it  changes  its  direction  and  curves  slightly 


THE  VASCULAR  SYSTEM.  329 

to  the  rig-ht,  so  that  it  finally  terminates  on  the  body  of  the 
fourth  lumbar  vertebra,  usually  to  the  left  of  the  mid-line,  by 
dividing"  into  the  two  common,  or  primitive,  iliac  arteries. 
This  position  is  indicated  by  a  line  drawn  from  the  highest 
point  of  the  crest  of  the  ilium  of  one  side  to  the  same  point  of 
the  opposite,  or  by  a  point  selected  half-an-inch  below  and  to 
the  left  of  the  umbilicus.  In  addition  to  the  curvature  to  the 
left,  it  also  is  sligfhtly  convex  forward,  conforming-  to  the  lum- 
bar portion  of  the  spine.  Owing"  to  the  larg"e  size  and  g^reat 
number  of  the  branches  g"iven  ofiF,  it  is  gfreatly  reduced  in  size 
at  its  termination. 

Relations,  Posteriorly  this  artery  rests  upon  the  front  of  the 
bodies  of  the  lumbar  vertebrae;  but  at  several  points  it  is  sepa- 
rated from  these  vertebra?  by  intervening"  structures.  Oppo- 
site the  second  lumbar  vertebra  is  the  commencement  of  the 
thoracic  duct,  the  receptaculuni  chyli;  and  throug-houtits  course 
are  found,  passing  behind  it,  the  left  lumbar  veins,  opposite 
the  corresponding  vertebras,  as  they  mike  for  their  points  of 
entrance  into  the  inferior  vena  cava.  Above,  to  the  left,  are  the 
left  crus  of  the  diaphragm  and  a  portion  of  the  sympathetic 
system,  the  left  semilunar  ganglion;  to  the  right,  the  right  crus 
of  the  diaphragm  and  a  portion  of  the  S3^mpathetic,  the  right 
semilunar  ganglion,  the  right  vena  az3'gos,  and  thoracic  duct, 
while  throughout  the  course  of  the  vessel  the  inferior  vena  cava 
lies  upon  its  right.  In  front  is  the  stomach.  Opposite  the 
apper  border  of  the  stomach  one  of  the  largest  branches  of  the 
abdominal  aortaarises,  the  C(jeliac  axis;  and  this  is  surrounded  by 
cords  of  the  sympathetic  system,  forming  the  solar  plexus  of 
nerves  with  its  two  semilunar  ganglia.  These  ganglia  are 
found  lying  to  the  front  and  lateral  aspects  of  the  commence- 
ment of  the  abdominal  aorta.  Below  this  comes  the  head  of 
the  pancreas,  and  immediately  below  this  the  left  renal  vein, 
tVe  transverse  portion  of  the  duodenum,  and  the  mesentery. 
Bilow  this  the  aorta  is  covered  at  the  front  and  at  the  sides  by 
thu  peritoneum  and  the  aortic  plexus  of  sympathetic  nerves. 
Another  of  its  branches,  the  superior  mesenteric,  lies  for  a 
shfjrt  distance  in  front  of  it;  but  curves  to  the  left  to  become  a 
<listant  relation   of  the  arterv.     Ccmvolutions  of  the  small  in- 


330  DESCRIPTIVE  ANATOMY. 

testines  cross  ov^er  the  front  of  the  vessel,  and  are  separated 
from  it  by  the  peritoneum,  which  covers  it  throughout,  the 
aorta  lying-  behind  the  peritoneum. 

Branches. 

(  Phrenic  (  Coeliac  Axis 

Parietal  -;  Sacra  Media  Visceral  -  Superior  Mesenteric 

(  Ivumbar  (  Inferior  Mesenteric 

;  Spermatic 
Genito-Urinary  -  Renal 

(  Suprarenal. 

The  brancJies  of  the  abdominal  aorta,  nine  in  number,  are 
arranged  in  three  sets  :  those  distributed  to  the  abdominal 
wall,  the  Parietal  Branches  ;  those  to  the  Abdominal  Viscera, 
the  organs  of  digestion,  and  those  accessory  thereto  ;  and 
those  distributed  to  the  genito-urinary  organs. 

The  Parietal  Branches. 

Phrenic  Sacra  Media  Lumbar 

The  ■phrenic  are  a  pair  of  small  arteries,  arising  from  the 
aorta  soon  after  it  enters  the  abdomen.  Their  manner  of 
origin  is  variable.  They  may  arise  by  a  common  trunk  ;  they 
may  arise  separately  from  the  aorta  ;  or,  in  some  cases,  one 
will  arise  from  the  aorta  and  the  other  from  one  of  the  adja- 
cent arteries,  most  frequently  the  renal.  Each  artery  runs 
backward  and  outward  on  the  under  surface  of  the  diaphragm 
Below  the  oesophageal  opening  they  divide  into  two  branches, 
one  of  which  encircles  this  opening  anastomosing  with  its 
fellow  of  the  opposite  side,  and  furnishing'  the  arterial  supply 
for  a  large  part  of  the  central  tendon  of  the  diaphragm. 
The  other  and  larger  branch  passes  outward  on  the  conca\e 
under  surface  of  the  muscle,  supplies  the  muscular  fibre,  ard 
inosculates  with  the  musculo-phrenic  branch  of  the  internil 
mammary,  and  with  the  other  diaphragmatic  arteries. 

The  lumbar  arteries  are  four  or  five  pairs  of  small  branches, 
which  spring  successively  from  the  back  of  the  aorta,  and 
run  outward  to  ramify  in  the  broad  muscles  of  the  abdomen. 
These    vessels   pass    beneath    the    musculo-tendinous    arches 


THE  VASCULAR  SYSTEM.  331 

formed  by  the  tendinous  fibres  of  the  psoas  magnus  and  the 
concave  lateral  aspect  of  the  bodies  of  the  lumbar  vertebrae. 

They  resemble  in  direction  and  in  distribution  the  intercos- 
tal arteries.  Passing  in  this  way  beneath  the  psoas  ma^rnus, 
these  vessels  divide  into  an  anterior  branch,  which  corresponds 
to  the  intercostal  artery,  and  a  posterior  branch,  which  corre- 
sponds to  the  dorsal  division  of  the  intercostal.  These  poster- 
ior divisions  supply  the  small  arteries  of  the  bodies  of  the  verte- 
bra?; and,  continuing-  their  course,  g"ive  off  the  spinal  branches 
to  the  contents  of  the  spinal  canal,  while  the  remaining-  portion 
is  distributed  to  the  muscles  of  the  back.  The  larger  anterior 
division  passes  forward  in  the  broad  muscles  of  the  abdomen, 
inosculates  with  other  vessels  w^hich  supply  those  muscles, 
mainly,  for  the  upper  branches,  with  the  terminal  branches  of 
the  internal  mammary,  and  for  the  lower  lumbars  with  the 
branches  which  spring-  from  the  deep  epigastric  and  ilio 
lumbar. 

The  sacra  nicdia  is  a  somewhat  slender  branch,  which  arises 
just  at  the  bifurcation  of  the  aorta,  though  occasionally  from 
one  of  its  forks.  It  passes  dow^n  upon  the  front  of  the  sacrum, 
gives  off  branches  which  anastomose  with  the  lateral  sacral 
arteries,  and  continues  its  course  to  the  tip  of  the  coccyx,  ter- 
minating in  the  vascular  gland  found  in  that  situation,  which 
is  known  as  Luschka' s,  or  the  Coccyg-eal,  Gland. 

The  Visceral  Branches. 

Cfjeliac  Axis       Superior  Mesenteric      Inferior  Mesenteric 

The  Visceral  hra)iches  spring  from  the  abdominal  aorta  by 
three  trunks,  the  Cieliac  Axis,  and  the  Superior  and  Inferior 
Mesenteric. 

The  cueliac  axis  is  the  first  and  largest  of  these  trunks. 
It  is  about  half  an  inch  in  length.  It  arises  from  the  front  of 
the  abdominal  aorta,  near  its  commencement,  and  passes  di- 
rectly forward  to  break  up  into  three  terminal  branches,  the 
Gastric,  the  Splenic,  and  the  Hepatic. 

Relations.  The  artery  arises  just  opposite  the  head  of  the 
pancreas,  upon  which  it  rests.  In  front  of  it  is  the  lesser 
omentum;  and  to  the  right  is  the  lobus  Spigelii,  while  the  cords 


332  DESCRIPTIVE  ANATOMY. 

of  the  solar  plexus  surround  the  artery  in  every  aspect,  and  a 
semilunar  g-ang-lion  lies  upon  either  side.  Its  position  corres- 
ponds to  the  level  of  the  upper  border  of  the  stomach,  while 
immediately  below  it  and  almost  in  contact  with  it  is  the 
orig-in  of  the  next  branch,  the  superior  mesenteric.  On  the 
left  side  it  is  relation  with  the  cardiac  end  of  the  stomach. 

Branches. 

Gastric  Splenic  Hepatic 

The  g-astric  is  the  smallest  branch  arising-  from  the  coeliac 
axis.  It  passes  upward  and  to  the  left  until  it  reaches  the 
cardiac  end  of  the  stomach,  where  it  turns  to  the  rig-ht,  runs 
along-  the  lesser  curvature  between  the  two  layers  of  the  les- 
ser omentum  nearly  to  the  pylorus,  where  it  inosculates  with 
the  pyloric  branch  of  the  hepatic  artery.  Just  before  making- 
its  turn  to  the  rig-ht  it  g-ives  off  branches  to  the  larg-e  end  of 
the  stomach  ;  and  in  coursing-  along-  the  upper  border,  it  g-ives 
branches  which  pass  downward  to  both  the  anterior  and  pos- 
terior faces  of  that  org-an. 

The  Splenic  Artery. 

The  ^^/e;z/6' artery  is  the  larg-est  of  the  branches  arising- from 
the  coeliac  axis.  It  is  very  tortuous,  runs  directly  from  rig-ht 
to  left  along-  the  upper  border  of  the  pancreas  to  reach  the 
hilum  of  the  spleen,  where  it  splits  into  numerous  branches  to 
be  distributed  to  that  org-an.  As  it  courses  along-  the  pancreas, 
it  lies  behind  the  stomach  and  just  above  the  splenic  vein, 
which  lies  on  the  posterior  surface  of  the  pancreas  in  a  g-roove 
a  little  distance  below  the  artery. 

Before  reaching-  the  spleen,  the  artery  g-ives  off  a  number 
(five  or  six)  of  larg-e  branches,  which  pass  to  the  splenic  end 
of  the  stomach,  and,  under  the  nime  of  the  vasa  brevia,  inos- 
culate with  the  branches  of  the  g-astric  artery,  and  supply  the 
cardiac  or  splenic  end  of  the  stomach. 

As  it  passes  along-  the  upper  border  of  the  pancreas,  numer- 
ous small  pancreatic  branches  are  g-iven  off,  which  descend 
into  that  g-land.  One  of  them,  of  larg-er  size,  is  frequently 
individualized  as  the  pancreatica  magna. 


THE  VASCULAR  SYSTEM.  333 

One  of  its  terminal  branches,  the  g-astro-epiploica  sinistra, 
leaves  the  artery  near  the  spleen,  runs  to  the  right  alontr  the 
g-reater  curvature  of  the  stomach  between  the  layers  of  the 
g-reat  omentum,  and  about  the  middle  of  the  g-reater  curvature 
of  the  stomach  inosculates  w'xththQ  g-astro-cpiploica  dextra,  an 
indirect  branch  of  the  hepatic  artery.  From  this  artery,  the 
g-astro-epiploica  sinistra,  branches  ascend  to  both  faces  of  the 
stomach,  and  descend  to  supply  the  g-reat  omentum. 

The  Hepatic  Artery. 

The  hepatic  is  intermediate  in  size  between  the  gastric  and 
the  splenic.  Its  usual  course  is  to  pass  to  the  rig-ht  and  slig-ht- 
ly  upward,  then  make  an  abrupt  bend  and  pass  nearly  vertically 
upward  to  the  under  surface  of  the  liver,  where  it  divides  into 
two  branches,  one  to  each  lobe  of  the  liver,  hence  known  as  the 
rig-ht  and  left  hepatic  arteries.  This  artery  is  accompanied  by 
a  duct  and  a  vein.  The  three  structures  are  in  close  contact, 
the  duct  lying-  furthest  to  the  rig-ht  and  the  artery  to  the  left, 
while  opposite  the  interval  between  them,  and  on  a  plane  pos- 
terior to  both,  is  found  the  portal  vein,  this  vein  being-  formed 
by  the  junction  of  the  superior  mesenteric  with  the  splenic. 
The  usual  manner  of  expressing-  the  description  is:  duetto  the 
right,  artery  to  the  left,  vein  between  and  behind  the  two. 
The  terminal  branches  of  the  artery  ramify  in  the  liver,  and 
furnish  the  arterial  blood  for  nourishing-  that  org-an. 

Besides  these  branches  it  produces  the  pyloric,  which  passes 
to  the  left  along-  the  lesser  curvature  of  the  stomach  until  it 
meets  the  g-astric  artery,  inosculates  with  that  vessel,  and  like 
it  is  distributed  to  both  faces  of  the  stomach. 

The  next  branch,  g-enerally  called  the  gastro-duodenalis, 
and  described  as  divided  into  the  paiicreatico-duodenalis  supe- 
rior and  the  gastro-epiploica  dextra,  is  preferably  described  as 
the  g-astro-epiploica  dextra.  This  artery,  arising-  from  the 
hepatic,  winds  around  the  g-reater  curvature  of  the  stomach, 
g-iving-  off  as  a  way-side  branch,  the  pancreatico-duodenalis 
superior.  This  small  branch  descends  to  the  interval  between 
the  duodenum  and  the  head  of  the  pancreas,  and  is  distributed 
to  both  of  these  structures  and  anastomoses  with  the  pancre- 


334  DESCRIPTIVE  ANATOMY. 

atico-duodenalis  inferior,  a  branch  of  the  superior  mesenteric; 
while  the  parent  trunk  continues  between  the  folds  of  the  g-reat 
omentum  until  it  inosculates  with  the  g^astro-epiploica  sinistra, 
forming  the  loop  from  which  ascending  branches  pass  to  both 
faces  of  the  stomach  and  descending  branches  pass  to  supply 
the  great  omentum. 

The  right  branch  of  the  hepatic  artery  likewise  gives  off  a 
branch,  called  the  cystic,  which  passes  to  the  gall  bladder  and 
divides  into  two  branches,  one  running  between  the  gall  blad- 
der and  the  under  surface  of  the  liver,  is  distributed  to  the  gall 
bladder  and  duct,  the  other  ramifies  on  the  free  surface  of  the 
gall  bladder.  This  branch  is'sometimes  described  as  a  third 
terminal  branch  of  the  hepatic  artery. 

It  will  be  seen  therefore  that  the  branches  of  the  coeliac  axis 
freel}^  anastomose  with  one  another,  the  splenic  anastomosing 
with  the  gastric  at  the  left  end  of  the  stomach,  and  with  the 
hepatic,  through  the  gastro-epiploica  dextra,at  the  middle  of  the 
greater  curvature.  The  hepatic  anastomoses  by  its  pyloric 
branch  with  the  gastric  on  the  upper  curvature,  and  with  the 
splenic  on  the  lower  curvature. 

Superior  Mesenteric. 

The  superior  niesenteric'v^  a  large  vessel,  which  arises  from 
the  front  of  the  aorta  just  below  the  coeliac  axis  and  behind  the 
head  of  the  pancreas.  Between  it  and  the  coeliac  axis  are  some 
branches  of  the  solar  plexus  of  nerves.  It  descends  between  the 
lower  border  of  the  pancreas  and  the  transverse  duodenum  to 
reach  the  right  iliac  fossa,  presenting  in  its  course  a  curve, 
whose  convexity  is  to  the  left,  lying  between  the  layers  of  the 
mesentery. 

Relations.  At  its  origin  this  vessel  lies  behind  the  head  of 
the  pancreas.  It  then  descends  for  about  an  inch  and  a  half, 
the  width  of  the  pancreas,  covered  by  that  structure.  It  ap- 
pears in  the  interval  between  the  lower  border  of  the  pancreas 
and  the  transverse  duodenum;  then  crosses  in  front  of  the 
transverse  duodenum;  and  from  that  point  onward  continues 
in  the  fold  of  the  mesentery,  moving  with  the  mesentery  in  the 
abdominal  cavity.  It  is  accompanied  throughout  by  the  supe- 
rior mesenteric  vein. 


THE  VASCULAR  SYSTEM.  335 

Branches. 

Vasa  Intestini  Tenuis  Colica  Dextra 

Ileo-Colic  Colica  Media 

Soon  after  its  orig-in  the  superior  mesenteric  artery  g-ives  off 
a  small  branch,  called  the  pancrcatico-duodoiaUs  inferior, 
which  passing-  upward  between  thepancreasand  the  duodenum, 
anastomoses  with  the  pancreatico-duodenalis  superior,  and  aids 
it  in  supplying-  the  descending-  duodenum  and  the  head  of  the 
pancreas.  The  remaining- branches  are  divided  into  two  sets, 
those  which  spring-  from  the  concave  and  those  which  spring- 
from  the  convex  aspect  of  the  vessel.  The  convexity  of  this 
vessel  looks  downward,  to  the  left,  and  slig-htly  backward;  the 
concavity  looks  upward,  to  the  rig-ht,  and  slig-htly  forward. 

Vasa  Intestini  Tenuis. 

From  the  convex  face  arise  a  number  of  branches,  varying- 
from  ten  to  eigfhteen  in  number,  the  vasa  intestini  tennis. 
These  branches  inosculate  so  freely  with  one  another  that  the 
circulation  in  the  intestinal  wall  is  still  abundantly  supplied 
thoug-h  a  larg-e  number  of  the  branches  may  be  ligfated. 
They  decrease  in  size  from  above  downward  ;  and  their 
distribution  is  not  quite  regfular,  thoug'h  the  plan  of  dis- 
tribution is  always  the  same.  Thus  each  branch  in  passing- 
outward  divides  into  an  ascending-  and  a  descending-  branch. 
These  branches  inosculate  with  the  corresponding-  branches 
above  and  below  so  as  to  form  a  series  of  arches.  From  these 
arches  are  g-iven  off  a  second  set  of  branches,  which  likewise 
divide  into  two,  and  inosculate  with  those  above  and  below, 
forming-  a  second  series  of  arches.  This  second  series,  in  like 
manner,  forms  a  third  ;  and  in  some  cases  as  many  as  five  or 
six  series  of  arches  may  be  discovered.  As  a  rule,  the  num- 
ber of  arches  does  not  exceed  three  ;  and  in  some  few  cases 
only  two  may  be  discovered.  No  matter  what  the  number  of 
arches,  from  the  terminal  arch  there  proceeds  a  set  of  straig-ht 
vessels,  the  vasa  recta,  which  pass  outward  on  both  faces 
of  the  small  intestine,  completely  encircling-  the  g-ut  and  inos- 
culate with  each   other,  so  that  both  in  its  circumference  and 


336  DESCRIPTIVE  ANATOMY. 

in  its  vertical  measurement  the  anastomoses  between  the  ver- 
tical arches  of  the  small  intestine  are  free  and  uninterrupted. 
From  the  concave  side  of  the  vessel  there  are  three  branches. 
In  the  order  in  which  they  arise  from  below  upward  they  are 
named  the  Ileo-colic,  the  Colica  Dextra,  and  the  Colica  Media. 
It  is  sometimes  seen  that  there  is  no  distinct  ileo-colic  artery  ; 
but  that  its  place  is  taken  by  the  termination  of  the  superior 
mesenteric  itself.  As  a  g^eneral  rule,  however,  the  superior 
mesenteric  terminates  by  becoming*  the  last  of  the  vasa  intestini 
tenuis  ;  and  the  ileo-colic  is  g"iven  off  from  the  concave  aspect 
of  the  vessel. 

Ileo-Colic. 

The  ileo-colic,  the  first  of  the  three  branches  to  arise  from 
the  concave  aspect,  is  distributed  somewhat  after  the  manner 
of  the  vasa  intestini  tenuis  ;  but  with  larg-er  arches,  or  rather 
with  loops  instead  of  arches.  Passing  downward  and  outward 
toward  the  right  iliac  fossa,  it  divides  into  an  ascending  and 
a  descending  branch.  The  descending  branch  passes  back  to 
inosculate  with  the  vasa  intestini  tenuis  or  with  the  termina- 
tion of  the  superior  mesenteric.  The  ascending-  branch  passes 
upward  to  reach  the  descending  branch  of  the  colica  dextra, 
thus  forming  two  large  loops,  from  which  the  straight  branches 
are  given  off  to  supply  the  termination  of  the  small  intestine 
and  the  beginning  of  the  large  intestine. 

Colica  Dextra. 

The  colica  dextra,  in  like  manner,  passing  straight  out- 
ward, divides  into  an  ascending  and  a  descending  branch,  the 
descending-to  anastomose  with  the  ascending  branch  of  the  ileo- 
colic, and  the  ascending-  with  the  descending  branch  of  the 
colica  media. 

Colica  Media. 

The  colica  media,  the  highest  of  the  three  branches,  passes 
downward  and  to  the  right,  with  the  intestine  in  the  anatomi- 
cal position,  and  divides  into  an  ascending  and  a  descending, 
or,  more  accurately,  right  and  left  branches,  the  descending, 
or  rig-ht,  branch  to  anastomose  with  the  ascending  branch  of 


THE  VASCULAR  SYSTEM.  337 

colica  dextra;  the  ascending,  or  left,  branch  to  inosculate  with 
the  colica  sinistra,  which  is  a  branch  of  the  inferior  mesen- 
teric. 

Prom  the  loops  formed  by  these  three  vessels  are  supplied 
the  termination  of  the  small  intestine,  the  csecum,  or  beg-iu- 
ing  of  the  large  intestine,  the  ascending  colon,  and  the  trans- 
verse colon  to  its  middle,  where  the  colica  sinistra  takes  up 
the  work. 

Inferior  Mesenteric. 

The  inferior  mesenteric  is  much  smaller  than  the  superior. 
It  arises  from  the  front  of  the  abdominal  aorta  near  its  termi- 
nation, and  descends  obliquely  to  the  left  iliac  fossa,  where  it 
finall}^  terminates  by  passing  over  the  brim  of  the  pelvis  under 
the  name  of  the  superior  hemorrhoidal  artery,  and  becoming 
a  relation  of  the  iliac  vessels. 

Branches. 

Colica  Sinistra  Sigmoid  Superior  Hemorrhoidal 

Colica  Sinistra. 

The  first  and  largest  branch,  the  colica  sinistra,  passes 
downward  and  to  the  left ;  and  divides  into  an  ascending  and 
a  descending  branch.  The  ascending  branch  inosculates  with 
the  left  branch  of  the  colica  media,  and  the  descending  w4th 
one  of  the  sigmoid  branches  of  the  inferior  mesenteric.  From 
these  two  loops  are  supplied  the  left  end  of  the  transverse 
colon  and  the  descending  colon. 

Sigmoid  Branches. 

The  sigmoid  are  several  branches,  varying  in  number  and 
in  size,  sometimes  there  being  but  a  single  branch,  which 
passes  outward  to  the  sigmoid  flexure  of  the  colon,  and  divides 
as  the  colica  sinistra  does,  the  ascending  branch  inosculating 
with  the  colica  sinistra,  while  the  descending  branch,  or  last 
branch  where  there  are  several,  inosculates  with  the  superior 
hemorrhoidal  or  termination  of  the  superior  mesenteric  itself. 
These  branches  supply  the  sigmoid  flexure  of  the  colon. 
Des  Anat— 22 


338  DESCRIPTIVE  ANATOMY. 

Superior  Hemorrhoidal. 

The  superior  hemorrhoidal d^^cenAs  along-  the  posterior  as- 
pect of  the  rectum,  lying- between  the  two  layers  of  peritoneum 
which  hold  the  rectum  in  position.  It  reaches  the  middle  of 
the  rectum,  where  it  anastomoses  with  the  other  hemorrhoidal 
arteries;  but  before  reaching-  this  point  it  has  received  the 
anastomosis  with  the  sigmoid  branches  of  the  inferior  mesen- 
teric. 

Summary. 

From  the  foreg-oing-  description  it  will  be  seen  that  the  sio7n- 
ach  is  supplied  with  blood  as  follows:  the  lesser  curvature  by 
the  loop  formed  between  the  g-astric  artery  and  the  pyloric 
branch  of  the  hepatic;  the  greater  curvature  by  the  rig-ht 
g-astro-eploica  f rom  the  hepatic  and  the  left  g-astro-eploica  from 
the  splenic;  the  splenic  end  of  the  stomach  by  the  vasa  brevia 
from  the  splenic  artery  and  by  branches  from  the  g-astric. 
All  of  these  branches  communicate  with  one  another  so  as  to 
render  the  stomach  a  net-work  of  arterial  branches. 

The  doudenuni  is  chiefly  supplied  by  the  pancreatico-duod- 
enalis  superior  of  the  hepatic,  which  vessel  is  aided  in  its  work 
by  the  pancreatico-duodenalis  inferior  from  the  superior 
mesenteric,  establishing-  a  communication  between  the  branches 
of  the  coeliac  axis  and  the  superior  mesenteric  artery. 

The  small  intestine  from  the  duodenum  to  near  the  larg-e 
intestine  is  supplied  by  the  vasa  intestini  tenuis  of  the  superior 
mesenteric.  The  termination  of  the  small,  and  the  beginning 
of  the  large,  intestine  are  supplied  by  the  ileo-colic  branch  of 
the  superior  mesenteric,  anastomosing-  with  the  termination  of 
the  superior  mesenteric  itself. 

The  ascending-  colon  is  supplied  by  the  loop  between  the 
colica  dextra  and  the  ileo-colic  below^  and  the  colica  media 
above. 

The  rig-ht  half  of  the  transverse  colon  is  supplied  by  the  loop 
betw^een  the  colica  media  and  the  colica  dextra,  the  left  half  by 
the  loop  betw^een  the  colica  media  and  the  colica  sinistra,  thus 
establishing- a  communication  between  the  superior  and  inferior 
mesenteric  arteries. 


THE  VASCULAR  SYSTEM.  339 

The  sigmoid  flexure  is  supplied  by  the  sig-moid  branches, 
after  anastomosing-  with  the  colica  sinistra,  and  by  the  superior 
hemorrhoidal  branch  of  the  inferior  mesenteric,  after  anasto- 
mosing* with  the  sig"moid  branches. 

Thus,  beg-inning-  w^ith  the  first  visceral  branch  of  the  abdo- 
minal aorta,  we  find  that  the  three  branches  which  supply  all 
of  the  hollow  viscera  and  many  of  the  solid  viscera  of  the  abdo- 
men not  only  communicate  with  the  branches  g-iven  off  from 
each  other,  but  communication  is  established  between  the  three 
by  the  inosculation  between  the  coeliac  axis  and  the  superior 
mesenteric  and  between  the  superior  mesenteric  and  the  infe- 
rior mesenteric. 

Genito-Urinary  Branches. 

Spermatic  (in  the  male).  Ovarian  (in  the  female). 

Renal  Suprarenal. 

Spermatic. 

The  Sper7iialic  are  a  pair  of  small  branches,  which  arise 
from  the  front  of  the  aorta,  and  descend  behind  the  peritoneum 
to  the  brim  of  the  pelvis,  one  on  either  side.  The  left  sperm- 
atic arises  at  a  lower  level,  and  is  consequently  a  little  shorter 
than  the  rig-ht.  Kach  artery  passes  across  the  external  iliac 
close  to  its  termination,  enters  the  deep  abdominal  ring-,  and 
traversing-  the  ing-uinal  canal,  leaves  the  abdomen  at  the 
superficial  ring-  to  accompany  the  other  elements  of  the  cord  to 
the  testicles,  where  it  is  distributed.  In  the  female  this  artery 
is  known  as  the  ovarian. 

Ovarian  Arteries. 

The  ovarian  artery  arises  like  the  spermatic,  and  its  rela- 
tions are  the  same  in  the  upper  part  of  its  course;  but  on  reach- 
ing- the  brim  of  the  pelvis,  it  crosses  the  common  iliac  artery, 
passes  into  the  folds  of  the  broad  lig-ament;  then  reversing-  its 
course,  runs  outward  to  be  distributed  to  the  ovary,  a  branch 
having-  been  g-iven  to  the  uterus,  to  the  laminai  of  the  broad 
lig-ament,  and  to  the  Fallopian  tube.  Other  branches  continue 
along  the  round  lig-ament,  throug-h  the  in^^uinal  canal,  to  the 
integ-ument  of  the  labia  and  g"roin. 


340  DESCRIPTIVE  ANATOMY. 

Suprarenal. 

The  suprarenal  ?iVQ  a  pair  of  small  arteries,  which  arise  from 
the  aorta  above  the  orig-in  of  the  renal,  and  pass  outward  on 
either  side  to  be  distributed  to  the  suprarenal  capsule.  These 
arteries  frequently  arise  from  the  renal  artery  itself  ;  and  g"eu- 
erally  there  are  two  or  three  on  either  side  of  the  body. 

Renal. 

The  renal  arteries  are  a  pair  of  larg-e  vessels,  which  spring- 
at  right  angles  from  the  abdominal  aorta,  rising  just  below 
the  superior  mesenteric.  They  pass  transversely  outward, 
with  the  vein  lying  in  front  of  them  and  the  ureter  behind 
them.  On  the  rignt  side  the  renal  artery  passes  behind  the 
vena  cava.  Just  as  they  reach  the  hilum  of  the  kidney  they 
break  up  into,  usually,  three  branches,  one  of  which  frequently 
goes  in  front  of  the  renal  vein.  They  enter  the  hilum  of  the 
kidney  to  be  distributed  to  that  organ.  The  left  renal  is  on 
a  somewhat  higher  plane  than  the  right,  owing  to  the  relative 
position  of  the  kidneys. 

The  Common,  or  Primitive,  Iliac  Arteries. 

^heco7n}Jion,  or  -primitive,  iliac  artery  oiQ2.<z\\  side  begins  by 
being  one  of  the  terminal  branches  of  the  abdominal  aorta,  where 
that  vessel  terminates  a  little  to  the  left  of  the  body  of  the 
fourth  lumbar  vertebra,  the  exact  point  of  division,  however, 
varying  slightly,  sometimes  as  much  as  an  inch.  From  this  ori- 
gin the  artery  passes  downward  and  outward  to  the  brim  of 
the  pelvis  to  terminate  on  the  side  of  the  disk  between  the  fifth 
lumbar  vertebra  and  the  sacrum  by  dividing  into  the  external 
and  internal  iliac  arteries.  The  average  length  of  each  artery 
is  about  two  inches ;  but  the  right  is  slightly  longer  than  the 
left,  owing  to  the  division  of  the  aorta  to  the  left  of  the  mid- 
line of  the  body. 

Their  relations  are  not  identical. 

Right  Common  Iliac. 

Relations.     The  right  common  iliac,  like  the  left,  lies  behind 
the  peritoneum.     It  is  usually  crossed  in  front  near  its  termi- 


THE  VASCULAR  SYSTEM.  341 

nation  by  the  right  ureter,  thoug-h  this  sometimes  extends  to 
the  external  iliac.  Convolutions  of  the  small  intestine  and 
sympathetic  nerves  are  also  found  in  front  of  it.  In  the  female 
it  is  crossed  by  the  ovarian  artery  in  front.  To  its  outer  side 
is  the  psoas  mag-nus  muscle.  Behind  it  is  the  left  common  iliac 
vein,  which  joins  the  rig-ht  common  iliac  to  the  outer  side  of 
the  beginning-  of  the  artery  to  form  the  inferior  vena  cava. 
Hence  its  relations  to  veins  are  quite  complex,  having"  at  its 
commencement  the  junction  of  the  two  veins  to  its  outer  side 
and  on  a  plane  posterior  to  it,  then  its  own  vein  external  and 
behind,  and  then  the  left  common  iliac  vein  directly  behind  it. 
It  lies  on  the  last  lumbar  vertebra. 

Left  Common  Iliac. 

Relations.  The  Left  common  iliac  i?,  crossed  in  front  by  the 
sigmoid  flexure  of  the  colon,  by  the  superior  hemorrhoidal 
artery,  and,  near  its  termination,  usually,  b}^  the  left  ureter. 
External  to  it  is  the  psoas  magnus  muscle.  Throughout  its 
course  its  vein  is  behind  and  internal  to  it.  It  lies  on  the  last 
lumbar  vertebra. 

The  common  iliac  arteries  give  off  no  branches. 

External  Iliac. 

The  external  iliac,  one  of  the  two  terminal  branches  of  the 
common  iliac,  commences  where  that  artery  bifurcates  on  the 
disk  between  the  fifth  lumbar  vertebra  and  the  sacrum  into  it- 
self and  the  internal  iliac.  It  continues  the  course  of  the  parent 
artery  downward  and  outward;  and  enters  the  thigh,  to  become 
the  femoral  artery,  by  passing  beneath  Poupart's  ligament  at 
a  point  midway  between  the  anterior  superior  spinous  process 
and  the  symphysis.  Its  course  aud  that  of  the  common  iliac 
may  be  indicated  by  drawing  a  line  from  a  point  just  to  the  left 
of  the  umbilicus,  the  point  of  bifurcation  of  the  abdominal  aorta^ 
to  a  point  midway  between  the  anterior  superior  spinous  pro- 
cess of  the  ilium  and  the  symphysis  pubis. 

Relations.  To  the  outer  side  of  the  artery  is  the  psoas  mag- 
nus muscle,  separated  from  it  by  the  iliac  fascia,  which  throws 
a  covering  over  the  artery  and  vein.   In  front  is  the  peritoneum, 


342  DESCRIPTIVE  ANATOMY. 

the  sub-peritoneal  fascia,  and  convolutions  of  the  small  intestine . 
The  vermiform  appendix  usually  lies  on  the  front  of  the  artery, 
separated  from  it  by  the  peritoneum.  Near  its  termination  the 
artery  is  crossed  in  front  by  the  g-enital  branch  of  the  g"enito- 
crural  nerve,  and  at  the  middle  by  the  spermatic  artery.  In 
the  female  of  course  there  is  no  spermatic  artery  to  cross. 
Sometimes  it  is  crossed  at  its  beginning-  by  the  ureter,  thoug-h 
that  structure  usually  crosses  the  termination  of  the  common 
iliac.  On  the  left  the  vein  is  throughout  an  internal  relation 
to  its  artery,  and  on  a  plane  posterior  to  it  until  it  reaches 
Poupart's  ligament;  on  the  right  the  vein  is  at  first  directly 
behind,  where  it  unites  with  the  internal  iliac  vein.  Then  it 
becomes  internal,  and  at  Poupart's  ligament  becomes  fully 
abreast  of  the  artery,  so  that  on  both  sides  at  Poupart's  liga- 
ment the  vein  is  internal  and  abreast  of  the  artery,  while  on 
the  left  side  it  remains  internal  and  on  a  plane  posterior 
throughout  the  remainder  of  its  course;  but  on  the  right,  when 
traced  from  below,  it  is  first  abreast,  then  internal  and  on  a 
plane  posterior,  and  then  directly  behind. 

Branches. 

Deep  epigastric  Deep  Circumflex  Iliac 

The  deep  e-pigastric  artery  arises  from  the  inner  side  of  the 
external  iliac  near  Poupart's  ligament.  It  first  runs  upward 
and  inward  on  the  posterior  face  of  the  anterior  abdominal  wall 
beneath  the  peritoneum  and  the  transversalis  fascia,  which  it 
raises  into  a  ridge.  It  then  enters  the  sheath  of  the  rectus 
muscle;  passes  upward,  first  between  the  sheath  and  the 
muscle,  and  then  punctures  the  fibres  of  the  muscle 
itself,  to  terminate  by  anastomosing  with  the  epigastric 
branch  of  the  internal  mammary,  thus  establishing  a  com- 
munication between  the  arteries  of  the  upper  and  the  arte- 
ries of  the  lower  extremity.  Soon  after  its  origin  it  gives 
off  a  communicating  branch  which  descends  to  the  obturator 
artery;  and,  in  many  instances,  takes  the  place  of  the  obturator 
artery  itself.  The  relations  to  the  abdominal  rings  will  be 
explained  in  connection  with  the  obturator  artery.  In  addition 
to  the  communicating  branch  to   the  obturator,   it  gives  off  a 


THE  VASCULAR  SYSTEM.  343 

branch  which  accompanies  the  cremaster  muscle,  muscular 
branches  to  the  rectus  muscle  itself,  a  pubic  branch  which 
passes  to  the  back  of  the  pubes  to  anastomose  with  its  fellow 
of  the  opposite  side,  and  cutaneous  branches,  which  pierce  the 
rectus  to  supply  the  skin  covering-  that  muscle. 

The  deep  circumflex  iliac,  the  second  branch  of  the  exter- 
nal iliac,  arises  from  the  outer  side  of  the  external  iliac  just 
above  Poupart's  ligament,  and  a  little  higher  up  than  the 
epigastric.  It  lies  beneath  the  peritoneum  ;  passes  upward 
and  outward  parallel  with  and  above  Poupart's  ligament  until 
it  reaches  the  crest  of  the  ilium,  where  it  usually  divides  into 
two  branches,  one  of  which  passes  upward  and  anastomoses 
with  the  ilio-lumbar,  gluteal  and  intercostal  arteries,  the 
other  continues  along  the  crest  of  the  ilium  to  anastomose 
with  the  lowest  lumbar  artery.  In  its  course  it  gives  off  mus- 
cular branches,  which  aid  in  supplying  the  broad  muscles  of 
the  abdomen,  and  cutaneous  branches,  which  pierce  to  the 
skin  and  anastomose  with  other  cutaneons  branches. 

The  Femoral  Artery. 

The/emoral  artery  is  the  continuation  of  the  external  iliac, 
commencing  where  that  artery  terminates,  beneath  Poupart's 
ligament,  at  a  point  midway  between  the  anterior  superior 
spinous  process  of  the  ilium  and  the  symphysis  pubis,  where 
it  can  be  felt  pulsating,  it  descends  the  front  of  the  thigh  to  its 
lower  third,  where  it  pierces  the  insertion  of  the  adductor 
magnus  muscle  to  reach  the  back  of  the  thigh  and  become  the 
popliteal.  As  long  as  it  lies  on  the  front  of  the  thigh,  that 
is,  for  the  upper  two-thirds  of  its  course,  it  is  known  as  the 
femoral  artery;  as  soon  as  it  reaches  the  lower  third  and 
appears  on  the  back  of  the  thigh  it  is  called  popliteal, 

A  line  drawn  from  about  the  middle  of  Poupart's  ligament  to 
the  inner  aspect  of  the  internal  condyle  will  indicate  the  course 
of  the  femoral  artery,  which  lies  behind  the  upper  two-thirds 
of  the  line. 

Relations.  For  the  first  half  or  third  of  its  course  the  femoral 
artery  issuperficial,  lying  in  Scarpa's  triangle,  having  the  sarto- 
rius  to  its  outer  side  and  the  adductor  longus  to  its  inner  side. 


344  DESCRIPTIVE  ANATOMY. 

It  enters  the  triano-le  about  the  middle  of  the  base  and  passing- 
tHrough  the  centre  leaves  it  usually  about  at  its  apex  by  passing- 
beneath  the  sartorius.  It  then  descends,  lying-  on  the  front  of 
the  insertion  of  the  adductor  long-us,  which  relation  it  maintains 
to  within  about  an  inch  or  so  of  its  termination,  and  for  that 
distance  it  is  separated  from  the  posterior  face  of  the  sartorius 
by  a  tendinous  arch  which  the  adductor  long-us  and  adductor 
magnus  throw  over  the  artery  to  the  vastus  internus;  so  that 
the  last  inch  or  two  of  the  femoral  artery  is  the  deepest  portion 
being  covered  by  the  skin,  superficial  fascia,  fascia  lata,  sarto- 
rius and  the  tendinous  arch  above  mentioned.  Throughout  its 
course  the  artery  lies  between  the  sartorius  and  adductor 
longus. 

In  the  upper  part  of  its  course  these  muscles  lie  one  on  either 
side,  while  below  the  sartorius  is  in  front  and  the  adductor 
longus  behind.  For  the  last  inch  or  two  the  sartorius  is  Sep- 
arated from  the  artery  by  the  tendinous  arch. 

Relations  to  Cords.  It  lies  in  a  sheath  which  also  contains 
the  femoral  vein.  At  Poupart's  ligament,  the  vein  is  internal 
and  abreast  of  the  artery;  but  as  it  descends,  passes  outvv^ard, 
so  as  to  get  first  behind  and  than  external.  In  the  upper  por- 
tion of  its  course  the  artery  has  from  one-fourth  to  one-half  an 
inch  from  its  outer  side  the  anterior  crural  nerve,  which 
here  divides  into  numerous  branches.  Of  these,  the  internal 
cutaneous  crosses  the  front  of  the  artery,  as  does  the  middle 
cutaneous  when  piercing  the  sartorius  muscle.  The  crural 
branch  of  the  genito-crural  nerve  crosses  the  artery  in  front 
in  its  upper  part.  The  long  saphenous,  accompanied  by  the 
nerve  to  the  vastus  internus,  descends  as  an  external  relation 
to  the  femoral,  which  relation  is  maintained  until  the  nerve  to 
the  vastus  enters  the  fibres  of  that  muscle.  The  saphenous, 
on  reaching  Hunter's  canal,  gets  directly  in  front  of  the  vessel 
but  not  in  its  sheath.  The  two  structures  then  separate,  the 
artery  passing  to  the  back  of  the  thigh,  while  the  nerve  con- 
tinues down  to  the  inner  side  of  the  knee  joint.  The  nerve  to 
the  pectineus,  when  that  musgle  is  supplied  by  the  anterior 
crural,  passes  behind  the  artery  in  the  upper  portion  of  the 
vessel.      At   a   variable   distance   from    Poupart's   ligament. 


THE  VASCULAR  SYSTEM.  345 

sometimes  not  more  than  half  an  inch,  while  occasionally  more 
than  two  inches,  there  arises  a  larg-e  trunk,  known  as  the  Deep 
Femoral  or  Profunda  Femoris.  At  its  orig-in  this  vessel  is 
external  to  the  femoral;  but  quickly  chang-es  its  direction  to 
pass  downward  and  inward  and  become  a  posterior  relation, 
which  position  it  maintains  until  the  two  vessels  are  separated 
b}'  the  adductor  longfus  muscle.  Both  the  superficial  and  the 
deep  femoral  vessels  are  accompanied  by  their  veins.  The 
relations  between  these  structures  is  usually  that  the  two  veins 
are  interposed  between  the  two  arteries  so  that  a  cross-section 
of  the  limb  would  exhibit  from  before  backward,  femoral 
artery,  femoral  vein,  profunda  vein,  profunda  artery.  It 
should  be  remembered,  however,  that  in  a  large  number  of 
cases  (probably  as  many  as  one-fourth)  the  relation  is,  femoral 
arter3%  femoral  vein,  profunda  artery,  profunda  vein. 

Branches. 

Superficial  Epigastric  Deep  External  Pudic 

Superficial  Circumflex  Iliac  Profunda  Femoris 

Superfi.cial  External  Pudic  Anastomotica  Magna 

Muscular 

Soon  after  its  commencement  the  femoral  artery  gives  oif 
four  small  branches  ;  the  Superficial  Epigastric,  the  Super- 
ficial Circumflex  Iliac,  the  Superficial  External  Pudic,  and 
the  Deep  External  Pudic.     These  are  all  cutaneous. 

The  superficial  cpig-astric  frequently  arises  by  a  common 
trunk  with  the  superficial  circumflex  iliac.  It  first  passes 
upward  and  inward,  then  continues  its  course  nearly  directly 
toward  the  umbilicus,  lying  beneath  the  skin  and  superficial 
fascia.  It  is  distributed  to  the  skin  near  the  lower  portion  of 
the  abdominal  wall  ;  and  anastomoses  with  the  cutaneous 
branches  of  the  deep  epigastric. 

The  superficial  circiunfiex  iliac,  arising  either  in  common 
with  the  superficial  epigastric,  or  separately  from  the  femoral, 
pisses  upward  and  outward,  parallel  with  Poupirt's  ligament, 
toward  the  crest  of  the  ilium.  It  supplies  the  superficial 
inguinal  glands,  the  skin  from  the  upper  front  portion  of  the 
thigh  ;  and  inosculates  with  the  superficial  branches  of  the 
deep  circnmflex  iliac. 


346  DESCRIPTIVE  ANATOMY. 

The  superficial  external  ■pitdic  arises  from  the  inner  aspect 
of  the  femoral,  and  passes  in  front  of  the  femoral  vein  toward 
the  g-enital  organs.  This  artery  either  passes  through  the 
fascia  lata  or  through  the  cribriform  fascia  covering  the  saphe-^ 
nous  opening.  It  passes  to  the  skin  covering  the  pubes  and 
supplies  that,  one  branch  passing  along  the  dorsum  of  the 
penis,  while  the  other  branches  are  distributed  to  the  sacrotum 
in  the  male  and  the  labia  in  the  female. 

The  deep  external  pudic  sometimes  arises  in  common  with 
the  superficial  external  pudic,  runs  inward  behind  the  femoral, 
then  passes  across  the  pectineus  muscle  and  perforates  the 
fascia  lata  close  to  the  syoiphysis  pubis.  It  inosculates  with 
branches  of  the  superficial  perineal  artery,  and  supplies  the 
sacrotum  and  perineum  in  the  male  and  the  labia  in  the  female. 

Profunda  Femoris. 

At  a  variable  distance  from  its  commencement,  generally 
from  one  to  two  inches  though  sometimes  less  and  sometimes, 
more,  the  femoral  artery  gives  off  from  its  outer  posterior 
aspect  a  branch  called  the  profiinda  femoris  which  is  almost 
as  large  as  the  continuation  of  the  femoral  itself.  The  direction 
of  the  profunda  is  for  a  short  distance  downward  and  outward, 
then  curving  inward,  almost  immediately  after  its  origin,  it 
descends  vertically  lying  behind  the  femoral  artery  and  having 
no  muscle  interposed  between  them  until  the  two  reach  the 
upper  edge  of  the  adductor  longus  which  muscle  thence  forward 
separates  them,  the  femoral  passing  down  on  its  front  and  the 
profunda  behind  it  for  some  distance  and  then,  perforating  the 
adductor  raagnus,  passes  to  the  back  of  the  thigh  where  it  is 
distributed. 

The  profunda  artery  is  contained  in  a  sheath  in  which  lies 
also  its  vein,  which  is  in  front  of  the  artery.  As  the  profunda 
descends  behind  the  femoral  it  is  separated  from  it  by  two. 
veins,  profunda  and  femoral;  so  that  from  the  origin  of  the 
profunda  down  to  the  adductor  longus  muscle,  the  structures 
lie  in  the  following  order  from  before  backward:  femoral  artery,, 
femoral  vein,  profunda  vein,  profunda  artery. 


THE  VASCULAR  SYSTEM.  347 

Branches  of  the  Profunda. 

External  Circumflex  Internal  Circumflex 

Three  Perforating- 

The  extcDial  circumflex  arises  early  from  the  profunda  and 
passes  outward  around  the  upper  extremity  of  the  femur,  g-iv- 
ing*  off  two  sets  of  branches,  one  ascending*  to  the  g-luteal  region 
and  the  other  descending-  to  the  outer  aspect  of  the  thig-h  and 
knee-joint.  These  branches  supply  the  muscles  on  the  outer 
front  aspect  of  the  thigh,  anastomosing- above  with  the  g-luteal, 
behind  with  the  internal  circumflex,  perforating  and  sciatic  and 
below  with  the  superior  external  articular. 

The  internal  circumflex  arises  from  the  profunda  near  its 
commencement  and  is  much  smaller  than  the  external  circum- 
flex. It  passes  inward  around  the  upper  extremity  of  the  femur 
and  anastomoses  with  the  external  circumflex,  superior  perfo- 
rating- and  obturator.  In  addition  to  supplying  the  muscles  on 
the  inner  aspect  of  the  thig-h,  this  vessel  g-ives  a  branch  to  the 
hip-joint. 

The  three  perforating  arteries.  As  the  profunda  femoris  is 
descending-  it  g-ives  off  in  succession  three  branches,  each  called 
perforating,  superior,  middle  and  inferior.  They  derive  their 
names  from  the  fact  that  they  perforate  the  adductor  magnus 
muscle  (the  superior  perforating"  the  adductor  brevis  also)  to 
reach  the  back  of  the  thig-h  and  supply  the  posterior  femoral 
muscles. 

Anastomotica  Magna. 

The  anastomotica  mag'na,  the  last  branch  of  the  femoral 
artery,  arises  from  it  just  as  that  artery  is  about  to  pierce  the 
adductor  magnus  and  descends  toward  the  knee  after  dividing 
into  a  superficial  and  a  deep  branch.  The  anastomotica  magna 
divides  into  a  superficial  branch  which  follows  the  long-  saph- 
enous nerve  beneath  the  sartorius  and  is  distributed  to  the  skin; 
and  a  deep  branch  which,  plunging-  into  the  vastus  internus 
muscle,  anastomoses  with  the  superior  internal  and  external 
branches  of  the  popliteal  and  with  the  recurrent  branch  of  the 
anterior  tibial. 


348  DESCRIPTIVE  ANATOMY. 

Besides  the  six  foreg-oing-  branches  the  femoral  artery  g-ives 
off  muscular  branches  to  the  muscles  in  its  course. 

The  Popliteal  Artery. 

The.  poftliteal  artery  ho.gm's,  by  being"  a  continuation  of  the 
femoral,  where  that  vessel  terminates  at  the  lower  third  of  the 
femur  by  passing-  to  the  back  of  the  thigfh  througfh  the  opening- 
in  the  adductor  mag-nus  muscle.  Its  course  is  downward  and 
outward  (the  obliquity  being-  g-reatest  at  first)  throug-h  the 
popliteal  space  to  the  lower  border  of  the  popliteus  muscle,  in 
front  of  the  tendinous  arch  of  the  soleus — a  point  which  corre- 
sponds to  the  junction  of  the  upper  fifth  with  the  lower  four- 
fifths  of  the  shaft  of  the  tibia — where  it  terminates  by  dividing- 
into  the  anterior  and  posterior  tibial  arteries. 

Relations.  The  artery  lies  in  the  popliteal  space  in  relation- 
ship with  the  muscles  forming-  its  walls, covered  by  the  popliteal 
fascia  and  surrounded  by  a  mass  of  fat  which  occupies  the  space. 
In  entering-  the  space  it  passes  beneath  the  inner  ham-stringf 
muscles,  and  hence  enters  below  the  upper  ang-le  of  the  space 
and  on  its  inner  wall.  The  biceps  is  to  its  outer  side  and 
diverg-es  from  the  artery  as  the  latter  descends.  The  heads  of 
the  g-astrocnemius  are  distant  external  and  internal  relations 
in  the  middle  of  the  vessel,  but  become  closer  and  superficial 
relations  towards  its  termination  owing-  to  their  converg-ence. 
The  artery  rests  first  on  the  lower  third  of  the  femur,  then 
on  the  posterior  lig-ament  of  the  knee-joint  and  then  on  the 
fascia  covering-  the  popliteus  muscle. 

Relations  to  Cords.  In  the  popliteal  space  are  found  the 
popliteal  artery  and  vein  and  the  internal  popliteal  nerve.  The 
artery  and  vein  enter  the  space  tog-ether,  on  its  inner  side  below 
the  superior  ang-le,  with  the  vein  behind  and  external  to  the 
artery  and  closely  adherent  to  it.  As  the  structures  descend, 
the  vein  winds  around  the  artery  and,  while  remaining-  behind, 
becomes  also  internal.  The  nerve  enters  the  space  at  its  apex 
and  is,  consequentl}^  external  to  the  artery  and  vein  as  well 
as  behind.  As  the  artery  is  inclined  outward  and  the  nerve 
inward  this  relation  chang-es  so  that  the  nerve  becomes 
internal  and  behind.     From   behind  forward,   throug-hout  the 


THE  VASCULAR  SYSTEM.  349 

course  of  these  structures,  the  order  is  nerve,  vein,  artery. 
In  the  upper  third  the  vein  and  nerve  are  behind  and  external, 
the  vein  closely  hug-g-ing-  the  artery;  in  the  middle  third  the 
vein  and  nerve  are  directly  behind;  in  the  lower  third  the  vein 
and  nerve  are  behind  and  internal.  The  g-reat  sciatic  nerve 
rarely  divides  at  the  apex  of  the  popliteal  space,  so  that  it 
is  more  correct  to  say  that  the  g-reat  sciatic  is  the  posteror- 
external  relation  for  the  upper  third  and  the  internal  popliteal 
is  the  relation  for  the  lower  two-thirds. 

Branches. 

Muscular  Inferior  External  Articular 

Superior  Kxternal  Articular  Inferior   Internal  Articular 

Superior  Internal  Articular  Azygfos  Articular 

The  muscular  branches  of  the  popliteal  consist  of  two  sets, 
superior  and  inferior.  The  superior  are  several  small  branches 
g-iven  off  to  the  ham-string*  inuscles,  while  the  inferior  consist 
usually  of  tv^^o  larg^e  branches  called  the  sural  which  are  dis- 
tributed to  the  two  heads  of  the  gfastrocnemius  muscle  and  to 
the  plantaris. 

The  Articular  Arteries,  five  in  number,  form  a  vascular 
zone  around  the  knee  joint,  aided  by  the  anastomotica  magna 
from  the  femoral,  the  external  circumflex  from  the  front  of  the 
femur,  and  a  recurrent  branch  from  the  anterior  tibial.  The}'" 
consist  of  two  sets,  superior  and  inferior,  each  set  consisting* 
of  two  arteries. 

The  superior  external  articular,  passes  beneath  the  tendon 
of  the  biceps  muscle,  around  the  outer  aspect  of  the  knee  joint 
above  the  external  condyle,  and  anastomoses  with  the  external 
circumflex  branch  of  the  profunda,  with  the  terminal  branch 
of  the  anastomotica  mag-na,  the  inferior  internal  and  external 
articular  arteries. 

The  superior  internal  articular,  passing"  beneath  the 
tendon  of  the  adductor  mag*nus,  winds  around  above  the 
inner  condyle  of  the  femur,  anastomosing*  with  the  anastomot- 
ica mag*na,  the  superior  external  articular,  and  the  inferior  in- 
ternal articular. 


350  DESCRIPTIVE  ANATOMY. 

The  inferior  external  articular  winds  around  the  head  of  the 
•fibula  below  the  outer  tuberosity  of  the  tibia,  anastomosing- 
with  the  superior  external  articular,  the  recurrent  from  the 
anterior  tibial,  and  the  inferior  internal  articular. 

The  inferior  internal  articular  passes  beneath  the  internal 
tuberosity  of  the  tibia,  anastomosing*  with  the  superior  internal, 
and  inferior  external  articular  arteries,  and,  across  the  patella, 
with  the  superior  external  articular. 

The  azygos  articular  consists  of  one  or  two  small  branches, 
which,  rising-  opposite  the  posterior  lig-ament  of  the  knee  joint, 
pierce  that  ligament  to  pass  into  the  interior  of  the  joint  and 
supply  the  structures  found  there. 

The  Posterior  Tibial  Artery. 

^\\^  -posterior  tibial  artery ,  one  of  the  two  terminal  branches 
of  the  popliteal,  begins  where  that  artery  terminates  at  the 
lower  border  of  the  popliteus  muscle,  beneath  the  tendinous 
arch  of  the  soleus  and  descends  the  back  of  the  leg-  with  a 
steady  inclination  inward  to  the  inner  aspect  of  the  os  calcis 
w^here  it  divides  midway  between  the  internal  malleolus  and 
posterior  tuberosity  of  the  os  calcis  into  the  internal  and  ex- 
ternal plantar  arteries. 

Relations.  The  posterior  tibial  artery,  for  about  the  upper 
two-thirds  of  its  course,  lies  deep,  covered  by  the  triceps  surae, 
but  for  the  rest  of  its  course  it  is  surperficial,  having-  emerg-ed 
to  the  inner  side  of  the  tendo  Achilles,  because  of  its  ow^n 
inward  inclination  and  because  of  the  narrowing-  of  the  triceps 
surae  to  a  tendon.  It  lies  on  the  tibialis  posticus,  the  flexor 
iDigas  digitoram,  the  tibia,  ani  on  the  ankle  joint. 

The  artery  is  accompanied  by  satellite  veins,  one  on  either 
side,  and  by  the  posterior  tibial  nerve.  The  nerve  for  the 
first  few  inches  of  the  artery  (at  the  lower  part  of  the  upper 
third  of  the  leg)  lies  to  the  inner  side  of  the  artery  and  then 
crosses  it  posteriorly  to  assume  a  continuous  external  relation. 
The  nerve  crosses  about  where  the  peroneal  branch  arises. 

The  relations  at  ankle  joint  from  within  outward,  first  is 
the  tendon  of  the  tibialis  posticus,  then  the  tendon  of  the  flexor 
longus    digitorum,  these    tendons    lying  in  the   same   groove, 


THE  VASCULAR  SYSTEM.  351 

next  comes  the  artery  with  a  satellite  vein  on  either  side,  then 
the  posterior  tibial  nerve  and  about  one-half  an  inch  more  ex- 
ternal is  seen  the  tendon  of  the  flexor  long-us  hallucis. 

Branches. 

Peroneal  Internal  Calcanean 

Terminal 

Besides  muscular  branches  to  the  muscles  in  its  course, 
and  its  two  terminal  branches,  the  posterior  tibial  produces 
two  branches,  peroneal  and  internal  calcanean.  One  of  its 
earliest  muscular  branches  g-ives  off  a  recurrent  branch  which 
passes  upward  to  the  knee-joint. 

The  peroneal  artery  is  nearly  as  large  as  the  continuation 
of  the  posterior  tibial,  and  arises  from  that  artery  high  up, 
near  its  origin,  the  distance  being  about  two  inches.  It  first 
passes  obliquely  downward  and  outward  to  the  origin  of  the 
flexor  longus  pollicis  muscle  and  then  descends  vertically 
beneath  that  muscle  to  terminate  on  the  outer  side  of  the  os 
calcis. 

Relations.  The  peroneal  in  the  upper,  oblique,  part  of  its 
course  is  covered,  like  its  parent,  by  the  triceps  surae  muscle, 
but  after  reaching  the  flexor  longus  pollicis  it  is  covered  by 
that  muscle  in  addition.  In  the  lower  part  of  the  leg  the 
difference  betw^een  the  two  arteries  in  depth  is  very  considerable, 
since  the  posterior  tibial  is  here  superficial  while  the  peroneal 
is  still  covered  by  the  flexor  longus  pollicis  and  the  tendo 
Achilles.  It  lies  on  the  tibialis  posticus  and  flexor  longus 
hallucis. 

Branches. 

Just  above  the  posterior  tuberosity  of  the  os  calcis  the  pero- 
neal and  posterior  tibial  arteries  are  connected  by  a  small 
transverse  communicating  branch.  The  peroneal  gives  mus- 
cular branches  to  the  muscles  in  its  course.  About  the  lower 
third  of  the  leg  the  peroneal  gives  off  a  large  branch  called 
the  anterior  peroneal,  which  pierces  the  interosseous  mem- 
brane to  reach  the  front  of  the  leg.  The  termination  of 
the  peroneal  is  distributed  on  the  outer  side  of  the  heel  by 
branches  called  external calcanea)i. 


352  DESCRIPTIVE  ANATOMY. 

The  internal  calcanean  branches  of  the  posterior  tibial  are 
three  or  four  in  number  and  are  distributed  to  the  inner  side 
of  the  heel.  They  anastomose  with  the  peroneal,  external 
calcanean,  internal  malleolar  and  plantar  arteries. 


The  internal  -plantar,  much  the  smiller  of  the  two  terminal 
branches  of  the  posterior  tibial,  beg^ins  where  that  artery 
bifurcates  midway  between  the  posterior  tuberosity  of  the  os 
calcis  and  the  internal  malleolus  and  passes  forward  alonof  the 
inner  side  of  the  sole  to  terminate  on  the  inner  side  of  the 
gfreat  toe  by  inosculating- with  the  dig-ital  branch  to  that  toe, 
having"  g-iven  oflF  muscular  branches  in  its  course. 

The  External  Plantar  Artery. 
The  external  plantar,  the  larg-er  and  more  important  of  the 
two  terminal  branches  of  the  posterior  tibial,  beg-ins  where 
that  artery  bifurcates  midway  between  the  posterior  tuberosity 
of  the  OS  calcis  and  the  internal  malleolus,  and  passes  forw^ard 
and  outward  between  the  first  and  second  layers  of  muscles  in 
the  sole  to  the  base  of  the  fifth  metatarsal  bone, where  it  turns 
inward  beneath  the  third  layer  of  the  muscles  to  cross  to  the 
inner  side  of  the  sole  and  terminate  there  at  the  posterior  ex- 
tremity of  the  first  interosseous  space  by  anastomosing"  with 
a  communicating  branch  from  the  dorsalis  pedis  artery.  That 
portion  of  the  artery  which  crosses  the  sole  from  the  outer  to 
the  inner  side  is  called  the  plantar  arch. 

Branches. 

Besides  muscular  branches,  the  external  plantar  gives  off 
the  following- :  digital  and  posterior  perforating. 

The  digital  branches  are  four  in  number.  They  run  for- 
ward to  the  cleft  between  the  toes  and  there  divide  to  supply 
plantar  collateral  branches  to  the  sides  of  the  toes,  except  the 
great  toe  and  the  inner  side  of  the  second  toe.  The  outermost 
of  the  four  is  appropriated  by  the  outer  side  of  the  little  toe. 
Just  before  the  digital  arteries  divide  at  the  clefts  of  the  toes, 
they  each  send  up  between  the  metatarsal  bones  a  branch  called 
anterior  perforating-,  to  open  into  the'  digital  branches  on  the 
dorsum  of  the  foot. 


THE  VASCULAR  SYSTEM.  353 

T\iQ posterior pcr/oraii)2g ,  three  in  number,  pass  up  between 
the  heads  of  the  three  outer  interosseous  muscles  to  anastomose 
with  the  metatarsea  artery  on  the  dorsum  of  the  foot. 

•  The  Anterior  Tibial  Artery. 

The  anterior  tibial  artery  beg-ins  where  the  popliteal  forks, 
at  the  lower  border  of  the  popliteus  muscle,  beneath  the  ten- 
dinous arch  of  the  soleus,  and  passes  directly  forward  between 
the  tibia  and  fibula  to  the  front  of  the  leg-  which  it  descends, 
lying-,  for  the  upper  two-thirds  of  its  course,  on  the  interos- 
seous membrane,  and  for  the  lower  third  on  the  front  of  the 
tibia,  to  terminate  on  the  middle  of  the  front  of  the  ankle-joint, 
beneath  the  annular  lig-ament,  by  assuming-  the  name  of 
dorsalis  pedis. 

Relations.  The  anterior  tibial  is  divided  into  three  portions, 
upper,  middle  and  low^er  thirds. 

In  its  upper  third  it  lies  on  the  front  of  the  interosseus 
membrane  between  the  tibialis  anticus  internally  and  the 
extensor  long-us  dig-itorum  externally.  In  its  middle  third  it 
still  lies  on  the  interosseous  membrane,  but  has  reached  the 
origin  of  the  extensor  proprius  pollicis  and  this  muscle  lies  on 
the  outer  side,  while  the  tibialis  anticus  still  remains  internal. 

In  its  lower  third  it  lies  on  the  front  of  the  tibia  and  is  crossed 
obliquely  by  the  tendon  of  the  extensor  proprius  pollicis, 
which  displaces  the  tibialis  anticus  and  becomes  the  internal 
relation,  while  the  extensor  long-us  dig-itorum  ag-ain  comes 
into  relation  with  it  externally. 

The  artery  is  accompanied  by  satellite  veins  and  the  anterior 
tibial  nerve.  The  nerve  is  at  first  to  its  outer  side;  then  for  a 
short  distance  in  front  of  it  and  then  ag-ain  to  the  outer  side. 

Branches. 

The  branches  of  the  anterior  tibial  artery  are  muscular,  a 
recurrent  branch,  which  ascends  to  the  front  of  the  knee 
throug-h  the  tibialis  anticus  muscle,  and  two  malleolar 
branches,  external  and  internal,  which  surround  the  tibia  just 
above  the  ankle-joint  and  supply  that  joint. 

Des  Anat— 23 


354  DESCRIPTIVE  ANATOMY. 

The  Dorsalis  Pedis  Artery. 

The  dorsalis  -pedis  artery  is  the  continuation  of  the  anterior 
tibial.  It  beo"ins  beneath  the  annular  lig*ament,  about  the 
middle  of  the  front  of  the  ankle-joint,  and  passes  forward 
along-  the  inner  side  of  the  dorsum  of  the  foot  to  terminate  at 
the  posterior  extremity  of  the  first  interosseous  space  by 
dividing-  into  the  dorsalis  hallucis  and  the  communicating-. 

Relations.  It  has  the  same  relations  to  muscles  and  cords  as 
the  lower  third  of  the  anterior  tibial.  To  its  inner  side  is 
the  extensor  proprius  pollicis  tendon,  to  its  outer  side  the 
extensor  long-us  digitorum,  and  near  its  termination  it  is 
crossed  by  the  tendon  of  the  extensor  brevis  dig-itorucn  to  the 
great  toe.  It  lies  between  satellite  veins  and  has  the  anterior 
tibial  nerve  to  its  outer  side. 

Branches. 

Tarsea  Dorsalis  Hallucis 

Metatarsea  Communicating- 

The  tarsea  branch  passes  outward  on  the  tarsus. 

The  metatarsea  branch  passes  outward  on  the  bases  of  the 
metatarsal  bones  and  receives  the  posterior  perforating- 
branches  from  the  plantar  arch.  The  metatarsea  sends  for- 
ward three  branches  called  interosseous,  which  after  receiving* 
the  anterior  perforating  branches  of  the  plantar  digital  arte- 
ries, divide  at  the  clefts  of  the  toes  to  form  collateral  digital 
branches  for  the  dorsal  aspect  of  the  fifth,  fourth  and  third 
toes  and  the  outer  side  of  the  second  toe. 

The  dorsalis  hallucis  is  one  of  the  two  terminal  branches  of 
the  dorsalis  pedis, and  runs  forward  to  supply  dorsal  collateral 
digital  branches  for  the  great  toe  and  inner  side  of  the  second 
toe. 

The  communicating  passes  through  the  first  interosseous 
space  to  anastomose  with  the  termination  of  the  external  plantar, 
giving  oif  a  branch,  the  magna  pollicis,  which  passes  forward 
and  divides  to  form  plantar  collateral  digital  branches  for  the 
great  toe  and  inner  side  of  the  second  toe. 


THE  VASCULAR  SYSTEM.  355 

Internal  Iliac  Artery. 

The  Internal  Iliac,  one  of  the  two  terminal  branches  of  the 
common  iliac,  commences  where  that  artery  bifurcates  on  the 
side  of  the  disc  between  the  fifth  lumbar  vertebra  and  the 
sacrum,  and  passes  downward  into  the  pelvis  over  the  front 
of  the  sacro-iliac  symphysis  to  the  upper  marg-in  of  the 
g-reat  sacro-sciatic  notch,  where  it  divides  into  the  anterior 
and  posterior  trunks.  Its  leng-th  is  variable,  and  is  usually 
about  two  inches.      It  is  a  short  and  wide  trunk. 

Relations.  It  lies  behind  the  peritoneum,  has  the  ureter  upon 
its  front,  and  rests  behind  upon  the  lumbo-sacral  cord  and  the 
pvriformis  muscle  and  internal  iliac  vein.  On  the  leftside  it 
has  resting-  upon  it  the  end  of  the  sig^moid  flexure  of  the 
colon. 

The  distribution  of  the  vessel  is  to  the  viscera  and  walls  of 
the  pelvis;  and  with  few  exceptions  it  will  be  found  that  the 
parietal  branches  spring-  from  the  posterior,  while  the  visceral 
are  the  offspring-  of  the  anterior  trunk.  The  hypogastric  ar- 
tery of  the  foetus  is  a  branch  of  the  internal  iliac.  It  is  nearly 
obliterated  after  birth,  becoming-  an  impervious  cord  from  the 
bladder  to  its  point  of  attachment  to  the  abdominal  wall  ;  but 
from  the  internal  iliac  to  the  wall  of  the  bladder  the  artery  is 
pervious,  and  carries  some  of  the  arterial  supply  of  that 
viscus. 

Branches  of  the  Anterior  Trunk. 

Hypog-astric  Obturator 

Inferior  Vesical  Ischiatic 

Middle  Hemorrhoidal  Internal  Pudic 

Hypogastric. 

The  first  of  these  branches,  the  obliterated  hypog-astric, 
passes  from  the  front  of  the  anterior  trunk  to  the  posterior 
surface  of  the  bladder.  This  artery  conveys  but  a  small 
amount  of  blood,  which  is  transmitted  to  the  bladder  by  two 
small  vessels,  known  as  the  superior  and  middle  vesical  arte- 
ries.    Thev  are  distributed  to  the  apex  and  g-reater  portion  of 


356  DESCRIPTIVE  ANATOMY. 

tHe   body   of   the   bladder,    while   a   small   twig-  from   one  is 
generally  g-iven  to  the  vas  deferens. 

Inferior  Vesical. 

The  inferior  vesical,   spring-ing-  directly  from  the  anterior 

trunk  is  distributed  to  the  base  of  the  bladder,  and  in  the  male 

subject,  passes  forward  also  to  the  prostate  g-land  and  to  the 

seminal  vesicles. 

Middle  Hemorrhoidal. 

The  next  branch,  the  middle  hemorrhoidal,  which  frequently 
arises  in  common  with  the  inferior  vesical,  pisses  to  the  rectum, 
and  supplies  the  middle  portion  of  that  g-ut,  anastomosing- 
above  with  the  superior  hemorrhoidal  and  below  with  the  infe- 
rior hemorrhoidal  branches  of  the  internal  pudic. 

Obturator. 

The  obturator  is  the  larg-est  of  the  way-side  branches  of  the 
anterior  trunk.  It  is  very  variable  in  its  orig-in.  Generally 
the  product  of  the  anterior  trunk,  it  sometimes  spring-s  from  the 
deep  epig-astric  branch  of  the  external  iliac;  and  in  a  few  cases 
may  be  found  arising  from  the  posterior  trunk  of  the  internal 
iliac.  Its  usual  course  is  to  pass  along  the  wall  of  the  pelvis 
just  below  its  brim,  accompanied  by  the  obturator  vein  and 
nerve,  the  nerve  lying  above  the  artery  and  the  vein  below. 
It  lies  behind  the  peritoneum,  between  it  and  the  parieta 
pelvic  fascia,  reaches  the  upper  margin  of  the  thyroid  foramen, 
and  leaves  the  pelvic  cavity  by  passing  through  this  foramen 
in  an  opening  left  above  the  obturator  membrane.  While  in 
the  pelvic  cavity  it  gives  off  a  small  branch,  which  passes  into 
the  iliac  fossa  to  supply  the  bone,  and  a  minute  twig  which 
ramifies  upon  the  posterior  face  of  the  pubic  arch,  anastomo- 
sing there  with  the  pudic  branch  of  the  deep  epigastric.  After 
emerging  from  the  pelvic  cavity,  it  divides  into  two  branches, 
external  and  internal.  Of  these  the  external,  which  is  the 
larger,  skirts  the  outer  margin  of  the  obturator  foramen,  and 
divides  into  two  branches,  one  of  which  anastomoses  with  the 
internal  division  of  the  obturator  and  the  other  with  the  inter- 
nal circumflex,  the  artery   supplying  the  muscles  around  the 


THE  VASCULAR  SYSTEM,  357 

tuberosity  of  the  ischium  in  its  course.  The  internal  branch, 
skirting-  the  inner  marg"in  of  the  obturator  foramen,  supplies 
the  muscles  around  that  foramen  and  the  abductor  muscles, 
anastomosing-  with  the  internal  circumflex  and  with  the 
external  division  of  the  obturator.  The  external  branch  also 
anastomoses  with  the  ischiatic. 

After  g-iving-  off  the  preceding-  branches,  the  anterior  trunk 
divides  into  two  terminal  branches,  the  ischiatic,  or  sciatic, 
and  the  internal  pudic. 

Ischiatic. 

The  ischiatic  arter}^  leaves  the  pelvis  throug-h  the  g-reat 
sacro-sciatic  foramen  below  the  pyriformis  muscle.  It  descends 
between  the  trochanter  major  and  the  tuberosity  of  the  ischium, 
crossing-  the  external  rotatersof  the  thig-h,  and  passing-  down- 
ward on  the  inner  side  of  the  g-reat  sciatic  nerve.  It  inosculates 
with  the  internal  circumflex  and  superior  perforating-  branch 
of  the  profunda,  and  g-ives  off  muscular  branches  to  the  mus- 
cles in  its  course.  Besides  these,  it  g-ives  coccyg-eal  branches 
within  the  pelvis,  which  pierce  the  g-reat  sacro-sciatic  lig-ament 
to  supply  the  g-luteus  maximus  muscle;  and  a  rather  larg-e 
branch,  called  \)i\^  inferior  gluteal,  passing-  to  the  deep  surface 
of  the  same  muscle;  an  articular  branch  to  the  hip  joint,  g-iven 
off  external  to  the  pelvis;  cutaneous  branches  to  the  integ-ument 
of  the  g-luteal  reg-ion;  and  a  branch  which  accompanies  the 
sciatic  nerve,  called  the  comes  nervi  ischiatici. 

Internal  Pudic. 

The  internal  pudic  is  the  second  and  smaller  of  the  two 
terminal  branches  of  the  anterior  trunk  of  the  internal 
iliac.  It  lies  in  front  of  the  ischiatic  ;  and  passes  down- 
ward over  -the  sacral  plexus  of  nerves,  parallel  with  that 
artery,  to  leave  the  pelvis  throug-h  the  g-reater  sacro- 
sciatic  foramen  below  the  pyriformis  muscle.  It  then  con- 
tinues its  course  to  the  spine  of  the  ischium,  winds  around 
that  process,  re-enters  the  pelvis  through  the  lesser  sacro- 
sciatic  foramen  lying-  about  an  inch  above  the  tuberosity  of 
the  ischium,  and  passes  upward  and  forward  along-  the  ramus 
of  the  ischium,  or  rather  the  obturator  internus  muscle,  held 


358  DESCRIPTIVE  ANATOMY. 

in  position  by  a  fold  of  the  pelvis  fascia,  until  it  reaches  a  point 
opposite  the  transversus  perinsei  or  near  the  central  point  of 
the  perineum,  where  it  divides  into  a  superficial  and  a  deep 
perineal  branch. 

The  su-perficial perineal  passes  forward  through  the  perineum 
as  far  as  the  scrotum.  At  the  upper  border  of  the  transversus 
perinsi  it  gives  off  a  branch  bearing-  the  same  name  as  that 
muscle,  which  crosses  on  that  muscle,  supplies  it  and  the 
adjacent  portion  of  the  skin,  and  anastomoses  with  its  fellow 
of  the  opposite  side. 

While  the  internal  pudic  is  still  in  the  pelvic  cavity  it  gives 
off  inferior  hemorrhoidal  branches.  These  branches  perforate 
the  pelvic  fascia,  which  holds  the  artery  in  position,  and  pass 
to  the  anus,  where  they  supply  the  sphincter  and  levator  ani 
muscles,  anastomosing  with  the  middle  hemorrhoidal  and  with 
the  vessels  of  the  opposite  side. 

The  dee^  -perineal  continues  the  course  of  the  internal  pudic, 
passing  between  the  two  layers  of  the  triangular  ligament,  and 
opposite  the  junction  of  the  crura  of  the  penis  divides  into  two 
branches,  the  dorsal  artery  of  the  penis  and  the  artery  of  the 
corpus  cavernosum. 

Prior  to  this  division  it  gives  off  a  large  branch ,  the  artery 
of  the  bulb,  which  enters  the  bulb  of  the  corpus  spongiosum 
and  is  distributed  to  that  structure.  It  is  a  very  short  trunk, 
which  passes  transversely  inw^ard  between  the  layers  of  the 
triangular  ligament  to  plunge  at  once  into  the  bulb  of  the  penis. 

The  artery  of  the  corpus  cavernosum,  one  of  the  terminal 
branches,  enters  the  crus  penis  on  its  inner  aspect,  and  is  dis- 
tributed in  that  body. 

The  dorsal  artery  of  the  penis,  the  other  terminal  branch, 
continues  upward  between  the  two  layers,  lying  in  the  sub- 
stance of  the  compressor  urethrae  muscle.  It  pierces  the 
anterior  layer  near  its  apex,  and  then  the  suspensory  ligament 
of  the  penis,  and  passes  along  the  dorsum  of  the  penis  to  the 
corona  to  anastomose  with  the  artery  of  the  opposite  side. 
In  this  course  it  is  accompanied  by  the  corresponding  nerve, 
which  lies  to  the  outer  side  of  the  artery.     This  artery  anas- 


THE  VASCULAR  SYSTEM.  359 

tomoses  with  the  deep  external  pudic  branch  of  the  femoral, 
which  has  been  knowm  to  tike  its  place. 

Branches  of  the  Posterior  Trunk. 

Ilio-Lumbar  Lateral  Sacral  Gluteal 

Ilio-Ivumbar 

The  ilio-lumbar  is  a  short  recurrent  branch,  which  arising* 
from  the  postero-external  part  of  the  internal  iliac,  passes 
upward  and  outward  beneath  the  common  iliac  artery.  It 
passes  between  the  lumbo-sacral  cord  and  the  obturator  nerve, 
and  then  beneath  the  psoas  mag-nus  muscle  ;  and  divides  into 
two  branches,  iliac  and  lumbar. 

The  iliac  brcuich  passes  betw^een  the  iliacus  internus  mus- 
cle and  the  iliac  fossa,  is  distributed  to  that  muscle,  and  sends 
a  nutrient  artery  to  the  bone. 

The  lumbar  branch,  passing-  beneath  the  psoas  mag"nus, 
supplies  that  muscle  and  the  quadratus  lumborum,  and  sends 
a  spinal  branch  into  the  foramen  between  the  last  lumbar 
vertebra  and  the  sacrum. 

Lateral  Sacral. 

The  lateral  sacral  are  a  pair  of  small  arteries,  the  superior 
of  which  enters  the  anterior  sacral  foramen,  where  it  commu- 
nicates wnth  branches  of  the  lumbar  arteries  above,  and  with 
branches  of  the  lower  lateral  sacral  below.  The  inferior  pass 
downward  on  the  front  of  the  sacrum,  and  send  a  branch  into 
each  anterior  sacral  foramen,  over  which  they  pass,  these 
branches  communicating"  with  one  another,  and  also  with  the 
superior  lateral  sacral  above. 

Gluteal. 

Th.t  finical  artery  is  a  continuation  of  the  posterior  trunk 
of  the  internal  iliac.  It  passes  backward  through  the  upper 
part  of  the  g-reat  sacro-sciatic  foramen  above  the  pyriformis 
muscle,  usually  piercing-  the  sacral  plexus  of  nerves.  After 
emerg-ing-  from  the  pelvis,  it  divides  into  two  branches,  a 
superficial  and  a  deep,  the  supe7'Jlcial  p3iS9,\ug  outward  between 
the  g-luteus  maximus  and  the  gluteus  medius  muscles  to  sup- 


360  DESCRIPTIVE  ANATOMY. 

ply  the  former,  and,  perforatino-  it,  to  be  distributed  to  the 
integument. 

The  dee^  branch,  itself  subdividing*  into  two,  runs  between 
the  g^luteus  medius  and  minimus,  and  g-ives  branches  to  these 
two  muscles.  The  superior  division  of  the  deep  branch  anas- 
tomoses with  the  circumflex  iliac,  and  with  the  external  cir- 
cumflex. 

The  inferior  division  anastomoses  with  the  external  circum- 
flex. 

The  superficial  branch  anastomoses  with  the  posterior 
branches  of  the  sacral  arteries. 

Internal  Carotid. 

The  Internal  Carotid  artery  is  one  of  the  two  terminal 
branches  of  the  common  carotid;  and  beg-ins  where  that  vessel 
terminates  on  the  upper  border  of  the  thyroid  cartilag-e  oppo- 
site the  transverse  process  of  the  fourth  cervical  vertebra,  and 
passes  upward  on  the  frout  of  the  transverse  processes  of  the 
three  upper  cervical  vertebrse  to  the  carotid  aperture  on  the 
basilar  surface  of  the  petrous  portion  of  the  temporal  bone. 
Entering-  at  this  foramen,  it  abruptly  chang-es  its  course  to 
pass  inward  and  forward,  with  a  slig^ht  inclination  downward, 
running-  in  the  carotid  canal,  to  an  aperture  of  exit  near  the 
apex  of  the  petrous  portion  of  the  temporal,  where  it  ag-ain 
chang-es  its  direction,  passes  upward  to  enter  the  cavity  of  the 
cranium,  turns  forward,  lying-  in  the  cavernous  g-roove  by  the 
side  of  the  sella  Turcica,  and  finally  passes  upward  beside  the 
anterior  clinoid  process,  and  divides  into  four  terminal  bran- 
ches. Anterior  Cerebral,  Middle  Cerebral,  Posterior  Commu- 
nicating-, and  Anterior  Coroid. 

Relations .  Its  relations  to  muscles  and  structures  throug-hout 
its  course  are  as  follows:  Behind  it  are  the  anterior  tubercles 
of  the  transverse  process  of  the  three  upper  cervicle  vertebrse, 
separated  from  the  artery  by  the  orig-in  of  the  rectus  capitis 
anticus  major.  In  front,  it  is  at  first  superficial,  being-  covered 
by  the  skin,  superficial  and  deep  fascia,  platysma,  stylo-hyoid 
and  dig-astric  muscles,  and  at  its  commencement  by  the  anterior 
border  of  the  sterno-cleido-mastoid.     As  it  ascends,  however, 


THE  VASCULAR  SYSTEM.  361 

it  passes  beneath  the  parotid  g-land,  the  stylo-g*lossus  and 
st3'lo-pharyng-eus  muscles  and  the  stylo-hyoid  lig-ament.  To 
its  inner  side  is  the  pharynx,  and  the  tonsil,  which  is  a  more 
distant  internal  relation. 

The  Relations  to  cords  are  numerous  and  important.  At  its 
commencement  the  internal  carotid  is  external  to  the  external 
carotid  artery  ;  but  as  it  ascends  the  neck  and  reaches  the 
stylo-hyoid  muscle  and  posterior  belly  of  the  dig-astric  muscle, 
the  internal  passes  behind  the  external  and  is  thenceforward 
separated  from  it  by  the  stylo-g-lossus  and  stylo-pharyng-eus 
muscles  and  stylo-hyoid  lig-ament,  and  b}^  the  oflosso-pharyn- 
^•eal  nerve,  and  the  pharyno-eal  branch  of  the  pneumog-astric. 
Through  the  greater  portion  of  its  course  the  internal  jugular 
vein  lies  to  its  outer  side,  as  does  the  pneumogastric  nerve  ; 
but  near  the  carotid  apertures  of  entrance  the  relations  are 
more  numerous  and  more  complex.  An  examination  of  the 
skull  will  show  that  the  jugular  foramen  is  directly  behind 
the  carotid  apertures  of  entrance,  and  that  the  anterior  condy- 
loid foramen  is  behind  and  internal  to  this.  Hence  the  rela- 
tions which  these  structures  bear  to  each  other.  At  the  point 
of  entrance  of  the  carotid  artery  the  internal  jugular  vein  and 
the  ninth,  tenth,  and  eleventh  nerves  lie  directly  behind  the 
artery,  while  the  twelfth  nerve  is  behind  and  slightly  inter- 
nal. The  ninth,  tenth  and  twelfth  quickly  emerge  between 
the  artery  and  the  vein,  while  the  eleventh  passes  behind  the 
vein.  The  relation,  then,  immediately  after  emergence  from 
their  respective  foramina  would  be  :  the  artery  the  most  inter- 
nal of  all  the  structures  l3^ing  against  the  wall  of  the  phar^'nx, 
the  most  external  the  internal  jugular  vein,  and  between  these 
the  ninth,  tenth,  and  twelfth  nerves.  At  the  lower  border  of 
the  stylo-glossus  muscle  the  glosso-pharyngeal  nerve  crosses 
over  the  front  of  the  artery,  and  ceases  to  be  a  relation. 

The  hypo-glossal,  or  twelfth,  nerve  now  becomes  an  antero- 
external  relation  until  it  reaches  the  lower  border  of  the  stylo- 
hyoid and  posterior  belly  of  the  digastric,  when  it  crosses  the 
artery  directly  in  front  to  reach  its  point  of  distribution,  while 
the  pneumogastric,  or  tenth,  continues  downward  as  an  ex- 
ternal relation,  lying  between  the  artery  and  the  vein.     Poste- 


362  DESCRIPTIVE  ANATOMY. 

riorly  the  artery  rests  upon  the  cervical  portion  of  the  sympa- 
thetic, which  separates  it  from  the  rectus  capitis  anticus 
major  muscle  The  interosseous,  or  petrosal,  portion  of  the 
artery  requires  no  description,  being-  imbedded  in  the  petrous 
portion  of  the  temporal  bone.  The  intra-cranial  portion,  lying- 
in  the  cavernous  sinus,  has  the  sixth  nerve  lying"  upon  its 
outer  side.  The  artery  is  covered  by  the  lining-  membrane  of 
the  sinus  ;  and  is  not  in  direct  contact  with  the  blood  which 
flows  throug-h  that  sinus. 

Branches. 
The  first portio)i  g"ives  off  no  branches.  Th.Q  second  portion 
produces  one  unimportant  branch,  the  tympanic,  which  passes 
to  the  tympanum.  The  third  portion  g-ives  origin  to  three 
branches.  Two  of  these,  the  arteria  receptacnli,  are  unim- 
portant and  are  distributed  to  the  cavernous  sinus  and  dura 
mater;  the  third  is  an  important  branch,  the  opthalmic  artery. 

The  Opthalmie  Artery. 

The  opthalmie  ar^'erv  spring's  from  the  internal  carotid  about 
the  termination  of  its  third  portion  and  passes  forward  into 
the  orbit  throug-h  the  optic  foramen,  first  lying  below  and 
external  to  the  optic  nerve,  then  crossing"  to  the  inner  side  of 
the  nerve  and  running  forward  along  the  inner  wall  of  the 
orbit  to  divide  at  the  internal  angle  of  the  orbit  into  two 
branches, /ro«/«/  and  nasal. 

Branches. 

The   branches  of  the  opthalmie  artery   are  ten   in  number. 

The  lachrymal  artery  runs  forward  along  the  outer  wall  of 
the  orbit  and  after  supplying  the  lachrymal  gland  passes  on 
to  the  upper  eye-lid.  It  gives  off  temporo-malar  branches 
which  pass  through  the  bone  to  the  temporal  muscle. 

The  supra  orbital  runs  forward  on  the  levator  palpebral 
muscle  and  escaping  to  the  forehead  through  the  supraorbital 
foramen,  is  there  distributed  by  a  superficialand  a  deep  branch, 
anastomosing  with  the  frontal. 

The  anterior  and  posterior  ethmoidal  arteries  escape  through 
the  anterior  and  posterior  ethmoidal  foramina,  and  are  distri- 
buted to  the  dura  mater,  ethmoidal  cells  and  nasal  fossae. 


THE  VASCULAR  SYSTEM.  363 

The  -palpebral  arteries,  superior  and  inferior,  arise  from 
the  opthalmic  near  its  termination.  The  superior  runs  out- 
ward on  the  upper  lid  near  its  free  edg-e,  between  the  orbicu- 
laris palpebrarum  and  the  tarsal  cartilage  and  is  there 
distributed;  the  inferior  does  the  same  for  the  lower  lid.  The 
two  sometimes  arise  by  a  common  trunk. 

Frontal. 

The/>'6>;//(2/,  one  of  the  two  terminal  branches  of  the  opthalmic 
artery,  emerges  at  the  inner  angle  of  the  orbit  and  ascends  to 
be  distributed  along  the  middle  of  the  forehead,  anastomosing 
with  the  anterior  branch  of  the  temporal,  with  its  fellow  and 
with  the  supra  orbital. 

Nasal. 

The  nasal,  the  other  terminal  branch  of  the  opthalmic  artery, 
emerges  at  the  inner  angle  of  the  orbit  and  is  distributed  along 
the  bridge  of  the  nose,  anastomosing  with  its  fellow  and  with 
the  facial  through  its  angular  and  transverse   nasal  branches. 

The  arteria  ce)itralis  retince  pierces  the  optic  nerve  and 
runs  forward  in  it  to  reach  the  retina  and  be  there  distributed. 

The  opthalmic  gives  off  numerous  muscular  branches  in  its 
course  which  are  divided  into  two  sets,  superior  and  inferior, 
the  superior  springing  by  one  trunk  and  the  inferior  by 
another.  Together  they  supply  the  muscles  in  the  orbital 
cavity.  They  are  very  irregular  in  number  and  in  point  of 
origin. 

The  ciliary  arteries  consist  of  three  sets,  viz  : 

1st.  Short  ciliary  branches,  which  are  numerous  small  ar- 
teries which  pierce  the  sclerotic  around  the  optic  nerve  and 
supply  the  choroid. 

2nd.  Long  ciliary,  which  are  two  branches  piercing  the 
sclerotic  on  opposite  sides  and  running  forward  between  it 
and  the  choroid  to  be  distributed  to  the  iris. 

3d.  Anterior  ciliary  h'CdLr\.z\\2.'^,  which  are  the  offspring  of 
muscular  branches  and  pierce  the  sclerotic  near  the  front  of 
the  eye  to  reach  the  iris. 

The  branches  from  the  fourth  or  cerebral  portion  are  four. 


364  DESCRIPTIVE  ANATOMY. 

Anterior  Cerebral  Artery. 

The  anterior  cerebral  artery,  one  of  the  terminal  branches 
of  the  internal  carotid,  runs  forward  in  the  long-itudinal  fissure, 
ascends  the  genu  of  the  corpus  callosum  and  runs  backward 
along-  that  body.  It  distributes  branches  to  the  frontal  and 
parietal  lobes  of  the  brain,  on  their  inner  face,  and  inosculates 
with  the  posterior  cerebral.  Its  branches  are  frequently  given 
the  names  of  the  convolutions  which  they  supply. 

Passing  from  the  anterior  cerebral  of  one  side  to  that  of  the 
other,  soon  after  their  origin,  is  a  communicating  branch 
called  the  anterior  communicating  artery. 

Middle  Cerebral  Artery. 

The  middle  cerebral,  arising  as  one  of  the  terminal  branches 
of  the  internal  carotid,  passes  outward  along  the  fissure  of 
Sylvius  to  be  distributed  to  the  anterior  and  middle  lobes  of 
the  cerebrum  and  to  the  convolutions  forming  the  island  of 
Reil.  This  artery  gives  off  two  sets  of  branches,  one  to  the 
cortex  and  one  to  the  ganglia  in  the  interior  of  the  brain.  The 
cortical  branches  are  distributed  over  the  outer  face  of  the 
frontal  parietal  and  temporo-sphenoidal  lobes,  and  receive 
the  names  of  the  convolutions  which  they  supply.  The 
ganglionic  branches  pierce  the  anterior  perforated  space  and 
are  distributed  in  the  interior  of  the  cerebrum.  An  important 
fact  concerning  these  branches  is  that  they  do  not  anastomose 
with  each  other  in  the  brain. 

Anterior  Choroid  Artery. 

The  anterior  choroid  pierces  the  base  of  the  brain  to  enter 
the  descending  cornu  of  the  lateral  ventricle  and  form  the 
choroid  plexus. 

Posterior  Communicating  Artery. 

The  j^osterior  communicati?i§  artery,  the  last  of  the  four 
terminal  branches  of  the  internal  carotid,  passes  backward  to 
anastomose  with  the  posterior  cerebral  of  the  basilar  artery. 


THE  VASCULAR  SYSTEM.  365 

From  this  artery  are  g-iven  off  g-ang-lionic  branches  which  pass 
throug-h  the  posterior  perforated  spot  to  the  interior  of  the 
brain. 

Circumscribing-  the  six-sided  space  at  the  base  of  the  brain 
is  a  series  of  arteries  and  their  communications  forming-  what 
is  called  the  vascular  circle  of  Willis.  Beg-inning-  in  front  we 
have  the  anterior  communicating-,  and,  following-  the  arteries 
back  on  one  side,  they  come  in  this  order,  anterior  cerebral, 
internal  carotid,  posterior  communicating-,  posterior  cerebral 
and  the  termination  of  the  basilar  artery.  Following-  them 
forward  from  the  basilar  artery  they  come  in  the  reverse  order. 


366  DESCRIPTIVE  ANATOMY. 


THE  VENOUS  SYSTEM. 

The  Veins  are  the  vessels  which  return  the  blood  which  the 
arteries  have  carried  to  the  capillaries.  Consequently  the 
venous  current  passes  in  a  direction  opposite  to  that  of  the 
arterial,  or  towards  the  heart,  opening-  mto  that  org^an  by  means 
of  two  main  trunks,  called  the  Superior  and  Inferior  Venae 
Cavae,  and  by  small  vessels  which  carry  the  venous  circulation 
of  the  heart  itself. 

The  veins  are  divided  into  two  sets,  the  superficial  and  the 
deep.  The  superficial  veins  are  found  between  the  layers  of 
snperficial  fascia;  and  ultimately  terminate  by  emptying  into 
the  deep  veins.  The  deep  veins  are  found  accompanying-  the 
arteries,  and  are  arrang-ed  in  two  forms  :  the  smaller  arteries 
are  accompanied  by  satellite  veins,  one  upon  either  side,  while 
the  larger  vessels  are  accompanied  by  a  sing-le  vein,  bearing- 
usually  the  name  of  the  artery  itself. 

The  venous  system  as  a  whole  is  very  much  larger  than  the 
arterial  system  as  a  whole;  and  this  statement  is  particularly 
true  of  the  veins  found  in  the  abdominal  cavity.  These  veins 
are  capable  of  being  greatly  dilated  upon  stimulation  of  the 
splanchnic  nerves,  so  that  it  is  possible  for  an  animal  to  bleed 
to  death  in  the  venous  channels  of  the  abdominal  cavity  with- 
out a  drop  of  blood  being  extracted  from  the  body,  the  veins 
dilating  to  such  an  extent  as  to  be  able  to  contain  all  of  the 
blood  of  the  system. 

As  a  rule  the  companion  veins  of  an  artery  receive  accessories 
corresponding  to  the  number  of  branches  which  are  emitted 
by  the  artery,  though  there  are  some  notable  exceptions  to  this. 

The  Veins  of  the  Lower  Extremity. 

The  Veins  of  the  Lozuer  Extremity  consist  of  two  sets, 
superficial  and  deep. 

The  deep  veins,  or  satellite  veins,  commence  in  the  sole  of 
the  foot  on  both  sides  of  the  plantar  arteries,  and  on  its  dorsal 
surface,  on  both  sides  of  the  dorsalis  pedis. 


THE  VENOUS  SYSTEM.  367 

The  companion  v^ins  of  the  internal  and  ext(Trnal  f>lantar 
arteries,  commencing'  respectively  on  the  inner  and  outer  side 
of  the  foot,  unite  where  the  posterior  tibial  artery  terminates 
to  form  two  companion  veins  for  the  posterior  tibial.  These 
veins  ascend,  lying-  one  upon  either  side  of  the  posterior  tibial 
artery,  and  recieve,  about  an  inch  below  the  begfinning  of  that 
vessel,  the  two  companion  veins  of  the  peroneal  artery,  which 
have  united  to  form  a  single  vein. 

The  satellite  veins  of  the  dorsalis  pedis  artery,  commencing 
on  the  dorsum  of  the  foot  at  the  g-reat  toe,  receive  the  veins 
from  the  tarsal  and  metatarsal  branches  of  that  artery  to  become 
at  the  front  of  the  ankle  the  companion  veins  of  the  anterior 
tibial.  These  veins  then  receive  the  accessory  veins  w^hich 
accompany  the  branches  of  the  anterior  tibial  artery,  and  con- 
tinue their  course  up  the  leg",  uniting  to  form  a  single  vein, 
which  passing-  above  the  interosseous  membrane,  joins  the 
branch  formed  by  the  satellite  veins  of  the  posterior  tibial 
artery  to  form  the  popliteal. 

The  Popliteal  Vein  then  passes  upward  accompained  by  the 
popliteal  artery.  It  lies  superficial  to  the  artery,  and  between 
that  structure  and  the  internal  popliteal  nerve,  lying  at  first 
behind  and  internal  to  the  artery,  directly  behind  it  in  the 
middle  portion  of  its  course,  and  behind  and  external  in  the 
beg-inning  where  the  femoral  artery  terminates  in  the  popliteal. 
It  receives  the  accessory  veins  which  accompany  the  five 
articular  branches  and  the  muscular  branches  given  off  by  the 
popliteal  artery,  and  becomes  the  femoral  vein  at  the  junction 
of  the  lower  third  with  the  upper  two-thirds  of  the  shaft  of 
the  femur. 

The  Femoral  Vein  then  accompanies  the  femoral  arter3% 
receiving-  in  its  course  the  veins  which  accompany  the  branches 
of  that  vessel.  It  lies  first  behind  and  external  to  the  femoral 
artery,  then  shortly  before  the  commencement  of  that  vessel 
directly  behind  it,  and  finally  internal  to  it,  so  thatat  Poupart's 
ligament  it  is  internal  and  fully  abreast  of  the  artery.  About 
an  inch  and  one-half  below  the  commencement  of  the  femoral 
artery,  it  g-ives  off  its  profunda  femoris  branch,  which  artery 
is  accompanied  by  its  own  vein  formed  by  the  various  satellite 


368  DESCRIPTIVE  ANATOMY. 

veins  accompanying-  branches  from  the  profunda  femoris.  At 
the  orio-in  of  the  profunda  this  vein  and  the  femoral  vein  unite, 
forming-  what  is  sometimes  called  the  Common  Femoral  Vein, 
which  lies  internal  and  abreast  of  its  artery  as  just  described. 
This  vein  at  Poupart's  lig-ament  terminates  by  becoming-  the 
External  Iliac  Vein.  Just  before  reaching-  Poupart's  lig-a- 
ment, the  femoral  vein,  lying-  then  opposite  the  saphenous 
opening-  of  the  fascia  lata,  receives  the  long-  or  internal, 
saphenous  vein  and  the  satellite  veins  w^hich  accompany 
the  superficial  branches  g-iven  off  from  the  femoral  in  this 
situation. 

After  chang-ing-  its  name  to  become  the  External  Iliac, 
the  vein  receives  the  companion  branches  of  the  deep  circum- 
flex, and  the  deep  epig-astric  branches  of  the  external  iliac 
artery.  It  then  passes  upward,  lying-  first  internal  and 
abreast  of  the  external  iliac,  and  then  internal  and  behind 
it  to  the  point  at  which  the  common  iliac  artery  divides  into 
its  two  terminal  branches,  opposite  the  intervertebral  disc 
between  the  fifth  lumbar  vertebra  and  the  sacrum. 

At  this  point  it  is  joined  by  the  internal  iliac  vein,  which  is 
made  up  of  a  larg-e  number  of  satellite  veins  accompanying-  the 
numerous  branches  of  the  internal  iliac  artery.  The  conflu- 
ence of  these  two  veins  forms  the  Common  Iliac,  which  vein 
is  found  lying-  first  directly  behind  its  artery,  then  external 
and  on  a  plane  posterior,  and  finally  external  to  the  common 
iliac  artery,  at  the  commencement  of  which  vessel,  opposite  the 
body  of  the  fourth  lumbar  vertebra,  it  unites  with  the  common 
iliac  vein  of  the  opposite  side  to  form  the  Inferior  Yena  Cava. 

This  description  applies  only  to  the  common  iliac  vein  of  the 
right  side  of  the  body.  0)1  the  left  side  the  external  iliac  vein 
is  internal  and  abreast  of  its  artery  at  Poupart's  lig-ament,  con- 
tinues internal,  but  on  a  plane  posterior  to  it,  up  to  the  bifur- 
cation of  the  common  iliac  artery,  passes  here  behind  the 
internal  iliac,  and  is  joined  by  the  vein  accompanying-  that 
artery,  forming-  the  Common  Iliac  Vein  of  the  left  side,  which 
vein  is  internal  to  the  common  iliac  artery  throug-hout  its 
course;  and  finally  passes  behind  the  rig-ht  common  iliac  artery 


THE  VENOUS  SYSTEM.  369 

to  join  with  that  vein  opposite  the  fourth  lumbar  vertebra  and 
form  the  inferior  vena  cava. 

Internal  Iliac  Vein. 

The  i)iter)ial  iliac  vein  is  formed  by  the  coalescence  of  the 
veins  accompanying-  the  branches  of  the  internal  iliac  artery, 

The  veins  of  the  visceral  branches  are  so  numerous  and  inter- 
secting that  they  form  plexuses.  The  vein  thus  formed 
ascends  behind  its  artery  and  unites  with  the  external  iliac 
vein  on  the  disk  between  the  fifth  lumbar  vertebra  and  the 
sacrum  to  produce  the  common  iliac  vein. 

The  Inferior  Vena  Cava. 

The  Inferior  Vena  Cava  then  continues  its  course,  lying- 
on  the  right  side  of  the  abdominal  aorta.  As  it  passes  upward, 
it  receives,  opposite  the  centre  of  the  body  of  each  lumbar  verte- 
bra, the  lumbar  veins  from  the  two  sides  of  the  body.  These 
veins  are  usually  four  or  five  in  number,  those  from  the  left 
side  passing  behind  the  abdominal  aorta  in  order  to  reach  the 
inferior  vena  cava.  About  opposite  the  lower  border  of  the 
second  lumbar  vertebra,  the  renal  veins,  formed  in  the  hilum 
of  the  kidneys,  pass  at  right  angles  into  the  inferior  vena  cava, 
the  vein  from  the  left  side  passing  across  the  front  of  the 
abdominal  aorta  generally,  though  occasionally  behind  it. 
The  vena  cava  itself  receives  the  suprarenal  veins,  and  con- 
tinuing its  course  upward,  passes  behind,  the  posterior  border 
of  the  liver,  upon  which  it  makes  a  deep  notch,  and  there 
receives  the  hepatic  veins.  It  then  pierces  the  diaphragm  on 
a  level  with  the  ninth  dorsal  vertebra,  but  on  the  right  side  of 
the  body,  through  the  highest  and  most  anterior  of  the  open- 
ings found  in  the  diaphragm;  and  entering  the  base  of  the 
heart  at  the  lower,  inner,  and  back  p«.rt  of  the  venous  auricle, 
pours  its  current  into  that  organ. 

The  Portal  System.  ' 

The  l)lood  which  is  poured  into  the  inferior  vena  cava  on  the 

posterior  border  of  the  liver  through  the  orifices  of  the  hepatic 

veins  is  derived  from  a  double  source,  a  part  of  it  coming  from 

the  veins  in  which  the  capillaries  of  the  hepatic  artery  termi- 

Des  Anat— 24 


370  DESCRIPTIVE  ANATOMY. 

nate,  while  a  part  of  it  is  the  product  of  the  portal  system  of 
veins,  which  drain  the  circulation  of  a  larg-e  portion  of  the 
alimentary  canal  into  the  liver,  where  the  veins  ramify  before 
uniting-  to  form  the  hepatic  veins.  It  will  thus  be  seen  that 
the  liver  receives  a  double  blood  supply,  one  portion  bein^ 
that  received  from  the  hepatic  artery,  the  ordinary  arterial 
blood,  which  is  intended  for  the  nutrition  of  the  liver  tissue 
itself  (parenchyma),  the  other  derived  from  the  alimentary 
canal  contains  that  blood  which  has  absorbed  the  products  of 
digestion,  and  which  passes  through  the  liver,  not  for  the 
purpose  of  nourishing  that  organ,  but  in  order  to  effect  the 
necessary  changes  in  the  blood  before  it  is  conveyed  to  the 
circulation. 

This  Portal  System  of  Veins  is  formed  in  the  following 
manner:  the  -portal  vein  commences  at  the  upper  border  of  the 
pancreas  by  the  union  of  the  splenic  and  the  superior  7nesen  - 
teric  veins.  The  splenic  vein,  before  uniting  with  the  superior 
mesenteric,  receives  behind  the  pancreas  the  inferior  mesenteric 
vein,  this  vein  conveys  the  return  circulation  from  the  sig- 
moid flexure  of  the  colon,  and  the  descending  colon.  The 
superior  mesenteric  vein  carries  the  return  circulation  from  the 
transverse  colon,  descending  colon,  coecum,  and  small  intes- 
tines. Hence  it  will  be  seen  that  the  greater  portion  of  the 
blood  from  that  part  of  the  alimentary  canal  which  serves  for 
the  digestion  of  food  is  carried  through  the  superior  mesenteric 
vein,  but  little  absorption  taking  place  in  that  part  of  the  large 
intestine  which  lies  below  the  formation  of  this  vein. 

After  the  splenic  and  superior  mesenteric  veins  have  united 
behind  the  upper  border  of  the  head  of  the  pancreas,  the  g'as- 
iric  veins,  one  of  which  accompanies  the  gastric  artery  and 
the  other  the  arch  formed  by  the  inosculation  of  the  gastro- 
epiploica  dextra  and  sinistra,  empty  into  the  portal  system, 
which  also  receives  the  small  vein  which  accompanies  the 
pancreatica  magna  artery  and  the  pancreatico-duodenalis  su- 
perior. The  vein  which  accompanies  the  pancreatico-duode- 
nalis inferior  empties  into  the  inferior  vena  cava  before  that 
reaches  the  splenic  vein. 


THE  VENOUS  SYSTEM.  371 

The  Sflenic  itself  is  formed  by  vessels  which  conve}^  the 
return  circulation  from  the  spleen;  and  also  receives  the  small 
veins  accompanying  the  various  branches  given  to  the  pan- 
creas and  the  vasa  brevia  of  the  stomach. 

The  Portal  Vein,  formed  in  this  way,  is  a  short,  wide  trunk, 
about  two  inches  in  length,  which  passes  upward,  lying  in  the 
right  edge  of  the  lesser  omentum.  It  lies  behind  the  hepatic 
artery  and  common  bile  duct ;  but  opposite  the  interval  be- 
tween these  tvv^o  structures,  so  that  in  naming  them  from 
right  to  left  the  order  would  be,  common  bile  duct,  portal  vein, 
and  hepatic  artery,  the  usual  statement  being,  duct  to  the 
right,  artery  to  the  left,  vein  between  and  behind  the  two. 
The  vein  now  enters  the  transverse  fissure  of  the  liver,  where 
it  breaks  up  into  numerous  branches,  which,  following  the 
lobules  of  that  organ  (see  histology  for  description),  unite 
into  minute  vessels,  which  in  their  turn  unite  again,  until 
finally  the  hepatic  veins  are  formed. 

These  veins,  three  or  four  in  number,  open  by  orifices 
which  remain  patulous  after  death,  into  the  inferior  vena  cava, 
as  it  is  coursing  along  the  posterior  border  of  the  liver. 

The  Spermatic  Veins. 

The  Spermatic  Veins  are  two  in  number,  right  and  left. 
They  begin  in  the  scrotum,  being  formed  by  the  plexus  of  veins 
surrounding  each  one  of  the  testicles.  These  veins  emerge 
from  the  back  of  the  testicle;  and  receiving  the  tributaries  from 
the  epididymus  forming  a  convoluted  plexus,  called  the 
Pa  mp  in  if  or  771  Plexus  (L.  Pa77ipi)ms,  a  tendril;  /or77ia,  like). 
They  then  pass  upward  with  the  other  elements  of  the  sper- 
matic cord.  Entering  at  the  superficial  abdominal  ring,  the}^ 
follow  the  course  of  the  spermatic  canal  to  enter  the  abdominal 
cavity  through  the  deep  abdominal  ring.  From  this  point  the 
courses  of  the  veins  on  the  two  sides  differ. 

0)1  the  7'ighi  side,  the  vein  passes  across  the  external  iliac 
artery,  gets  to  the  outer  side  of  that  vessel ;  and  passing  upward 
with  a  steady  inclination  inward,  terminates  by  entering  at  an 
acute  angle  into  the  inferior  vena  cava,  the  blood  from  the  sper- 
matic vein  going  in  the  same  direction  as  the  blood  from  the 
vena  cava. 


372  DESCRIPTIVE  ANATOMY. 

On  the  left  side,  it  crosses  the  termination  of  the  internal  iliac 
artery;  but  ascends  vertically,  and  empties,  not  into  the  vena 
cava,  but  into  the  left  renal  vein,  at  right  angles  to  that  vein, 
so  that  the  whole  current  of  blood  in  the  renal  vein  passes 
across  the  aperture  of  the  left  spermatic  and  retards  the  flow 
of  blood  from  this  vein.  It  is  for  these  anatomical  reasons 
that  enlargement  of  the  veins  of  the  left  testicle  and  scrotum 
so  frequently  occurs,  the  surgical  disease  known  as  variocele 
arising  from  this  cause. 

The  Superficial  Veins  of  the  Lower  Extremity. 

Returning  to  the  lower  extremity,  we  find  that  there  are 
certain  small  veins  belonging  to  the  superficial  system.  Those 
which  have  received  distinctive  names  are  two  in  number,  the 
short  and  the  long  saphenous.  They  commence  on  the  dorsal 
aspect  of  the  foot,  the  long  saphenous  on  the  inner  and  the 
short  saphenous  on  the  outer  side  ;  and  the  veinlets  which 
compose  them  inosculate  with  one  another  so  as  to  form  an  arch, 
extending  entirely  across  the  foot  near  the  web  of  the  toes. 

The  Short  Sa-phenous  Vein  can  be  traced  back  from  the  outer 
edge  of  the  little  toe  behind  the  external  malleolus,  where  it 
passes  to  the  postero-external  aspect  of  the  leg,  accompan3'ing 
the  nerve  of  the  same  name.  As  it  passes  upward,  it  gradually 
wnnds  to  the  middle  of  the  calf  of  the  leg,  and  there  lies  in  the 
groove  which  is  found  on  the  posterior  face  of  the  gastrocnemius 
muscle.  It  continues  its  upward  course  between  the  two  heads 
of  the  gastrocnemius,  and  terminates  by  emptying  into  the 
popliteal  vein. 

The  Long-  Saphenous  Vein  commences  on  the  inner  side  of 
the  great  toe.  It  passes  backward  along  the  inner  side  of  the 
arch  of  the  foot,  runs  across  the  front  of  the  internal  malleolus, 
passes  upward  on  the  inner  face  of  the  calf,  behind  the  internal 
condyle  of  the  femur,  until  it  reaches  the  junction  of  the  lower 
third  with  the  middle  third  of  the  thigh,  where  it  runs  slightly 
forward,  and  continues  its  upward  course  along  the  inner  front 
aspect  of  the  thigh  until  it  reaches  the  saphenous  opening  in 
the  fascia  lata,  where  it  pierces  the  cribriform  fascia,  and 
terminates  by  emptying  into  the  femoral  vein.     Occasionally 


THE  VENOUS  SYSTEM.  373 

before  emptying'  into  the  femoral  the  long-  saphenous  receives 
the  satellite  veins  of  the  superficial  branches  of  the  femoral 
artery;  and  more  frequently  these  branches,  four  in  number, 
terminate  by  opening"  directly  into  the  femoral  vein,  the  aper- 
tures which  they  make  through  the  fascia  covering-  the  saphe- 
nous opening"  g-iving-  it  its  cribriform  appearance. 

The  Veins  of  the  Upper  Extremity. 

The  Veins  of  the  Upper  Extremity,  like  those  of  the  lower, 
consist  of  a  superficial  and  a  deep  set ;  but  unlike  the  lower 
extremity,  the  superficial  veins  are  here  so  larg"e  and  so 
numerous  that  the  satellite  veins  are  small  in  size,  and  convey 
but  a  small  portion  of  the  return  circulation. 

The  deep  veins  commence  in  the  palm  of  the  hand.  They 
commence  as  the  companion  veins  of  the  superficial  palmar 
arch,  orig-inating-  in  veins  which  accompany  the  dig-ital 
branches  of  that  arch.  This  arch  receives  the  interosseus 
veins ;  and  forms  on  either  side  the  vena^  comites  of  the  ulnar 
and  radial  arteries. 

The  companion  veins  of  the  radial  and  ulnar  arteries  unite 
with  each  other  below  the  bend  of  the  elbow,  and  form  the 
two  satellite  veins  of  the  brachial  artery.  That  is,  the  satel- 
lite veins  of  the  radial  form  the  external  satellite  veins  of  the 
brachial,  while  the  satellite  veins  of  theulnar  form  the  internal 
satellite  veins  of  the  same  artery.  After  receiving-  superficial 
veins  and  tributaries  from  the  branches  of  the  brachial,  these 
two  satellites  pass  upward  to  the  lower  border  of  the  tendons 
of  the  latissimus  dorsi  and  teres  major  muscles,  and  there 
unite  to  form  the  Axillary  Vein,  which  follows  the  course  of 
the  axillary  artery,  lying-  to  its  inner  front  aspect  throug-hout 
the  course  of  that  vessel,  receiving-  tributaries  from  the  veins 
accompanying-  branches  of  that  vessel,  the  larg-est  and  most 
important  of  which  are  the  companion  veins  of  the  sub-scapular 
artery,  and  terminates  at  the  outer  border  of  the  first  rib  by 
becoming-  the  subclavian  vein.  This  vein  then  continues  its 
course  to  join  the  internal  jug-ular,  and  form  the  innominate 
vein. 


374  DESCRIPTIVE  ANATOMY. 

The  Superficial  Veins  of  the  Upper  Extremity. 

Anterior  Ulnar  Radial 

Posterior  Ulnar  Median 

Common  Ulnar  Basilic 

Cephalic  Median  Basilic 

Median  Cephalic  Subclavian 

The  Anterior  Ulnar. 

The  Anterior  Ulnar  Vein  begins  on  the  inner  front  aspect 
of  the  ulnar  side  of  the  hand  by  small  tributaries  which  come 
from  the  little  finger  and  inner  side  of  the  ring-  and  middle 
fingers.  Continuing  its  course  upward  it  receives  tributaries 
from  adjacent  portions  of  the  forearm  ;  and  about  an  inch  and 
one-half  below  the  elbow-joint,  unites  with  the  posterior  ulnar 
to  form  the  common  ulnar  vein. 

The  Posterior  Ulnar. 

The  Posterior  Ulnar  Vein  arises  near  the  back  of  the  little 

finger,  passes  upward  on  the  postero-internal  aspect  of  the 

forearm  ;  and    joins  the  anterior  ulnar  to  form  the   common 

ulnar. 

The  Common  Ulnar. 

The  Comvion  Ulnar  Fi?/;?  ascends  to  the  inner  side  of  the  front 

of  the  elbow  to  unite  with  the  median  basilic  vein  to  form  the 

basilic  vein. 

The  Radial  Vein. 

The  Radial  Vein  commences  on  the  outer  side  of  the  back 
of  the  hand,  receiving  tributaries  from  the  thumb,  index  and 
middle  fingers  ;  and  passing  upward,  winds  around  to  the 
front  of  the  forearm  about  at  its  lower  third.  It  then  con- 
tinues to  ascend  until  it  reaches  a  point  about  an  inch  below 
the  elbow  joint,  where  it  unites  with  the  median  cephalic  to 
form  the  cephalic  vein. 

The  Median  Vein. 

The  Median  Vein  is  a  small  vessel  which  receives  the  blood 
from  the  middle  of  the  palm  of  the  hand.     It  is  scarcely  per- 


THE  VENOUS  SYSTEM.  3/D 

ceptible  until  just  above  the  wrist  joint,  where  the  formation 
of  the  vein  may  be  said  to  take  place.  It  then  passes  directly 
upward,  lying"  on  the  middle  of  the  front  of  the  forearm  until 
it  reaches  a  point  about  an  inch  and  a  half  below  the  middle 
of  the  front  of  the  elbow  joint.  In  this  situation  it  divides 
into  two  branches,  an  internal  and  an  external,  named  respec- 
tiveh'  the  Median  Basilic  and  the  Median  Cephalic. 

The  Median  Basilic. 

The  MedicDi  Basilic  Vein  unites  with  the  common  ulnar, 
the  product  of  the  anterior  and  posterior  ulnar  veins,  to  form 
the  basilic. 

The  Median  Cephalic. 

The  Media)i  Cephalic  Vein  unites  with  the  radial  vein  to 
form  the  cephalic  vein. 

The  Basilic  Vein. 

The  Basilic  Veiii,  formed  below  the  elbow  joint  by  the 
union  of  the  common  ulnar  with  the  median  basilic,  passes 
upward  and  crosses  over  the  bicipital  slip  of  fascia  g-iven  off 
from  the  tendon  of  the  biceps  to  the  fascia  of  the  inner  side  of  the 
forearm.  It  then  lies  to  the  inner  front  aspect  of  the  brachial 
artery  to  about  the  middle  of  the  course  of  that  vessel,  sep- 
arated from  it  by  the  deep  fascia,  where  its  relation  is  chang-ed 
only  to  the  extent  of  lying-  beneath  the  investing-  fascia.  That 
is,  up  to  the  middle  of  the  brachial  artery  the  basilic  vein  is 
superficial  to  the  investing-  fascia ;  but  opposite  the  middle  of 
that  vessal  it  pierces  this  fascii,  and  becomes  deeper,  lying- 
still  to  the  inner  front  aspect  of  the  brachial  artery,  but  more 
nearly  on  the  same  plane  with  that  vessel.  It  finally  termi- 
nates by  uniting  with  the  internal  satellite  vein  of  the  brachial 
just  before  the  latter  unites  with  the  external  satellite  to  form 
the  axillary  vein.  Some  authorities  describe  the  basilic  as  re- 
ceiving- the  two  satellite  veins  of  the  brachial  and  becoming- 
the  axillary  vein. 

The  Cephalic  Vein. 

The  Cephalic  Vein,  formed  below  the  middle  of  the  elbow 
joint  by  the    union   of    the   radial    and    the    median    cephalic, 


376  DESCRIPTIVE  ANATOMY. 

passes  upward  and  outward  until  it  reaches  the  interval  be- 
tween the  brachialis  anticus  and  the  supinator  long-us  and  ex- 
tensor carpi  radialis  lonofior.  It  then  passes  upward  in  a 
g-roove  found  on  the  outer  aspect  of  the  arm,  caused  by  the 
bulg-ing-  of  the  biceps  anteriorly  and  the  triceps  posteriorly; 
and  continues  its  course  until  it  reaches  the  lower  edge  of  the 
deltoid  muscle,  when  it  turns  across  the  front  of  the  arm  to 
reach  the  interval  between  the  deltoid  and  the  pectoralis  major. 
After  .running-  in  the  g-roove  between  these  two  muscles,  it 
passes  over  the  fibrous-covered  interval  between  the  muscles 
and  empties  into  the  axillary  vein  just  before  its  termination 
in  the  subclavian.  Before  the  cephalic  vein  enters  the  axil- 
lary it  receives  a  communication  from  the  external  jug-ular 
vein  of  the  neck. 

The  Axillary  Vein. 

The  Axillary  Vein  is  formed  by  the  junction  of  the  brachial 
satellites  and  the  basilic  at  the  termination  of  the  axillary 
artery.  It  passes  upward  on  the  inner  front  aspect  of  the  ax- 
illary artery  throug-h  the  axillary  space,  receives  the  tributaries 
which  accompany  the  branches  of  that  vessel;  and  continually 
increases  in  size  until  it  reaches  the  outer  border  of  the  first 
rib  behind  the  junction  of  the  outer  third  with  the  inner  two- 
thirds  of  the  shaft  of  the  clavicle,  where  it  terminates  by 
becoming-  the  subclavian  vein. 

The  Subclavian  Vein. 

The  Subclavian  Vein  bears  the  same  relation  to  its  artery  that 
the  string-  bears  to  a  bent  bow.  Commencing-  at  the  outer  one- 
third  of  the  clavicle  on  the  anterior  border  of  the  first  rib,  it 
passes  horizontally  inward ,  lying-  below  and  on  a  plane  anterior  to 
the  corresponding-  artery,  so  that  it  is  anantero-internal  relation 
of  the  third  portion  of  the  subclavian,  and  an  antero-external 
relation  of  the  first  portion  of  the  subclavian,  being-  separated 
from  the  second  portion  by  the  interposition  of  the  scalenus 
anticus  muscle.  As  this  vein  passes  inward,  it  receives,  first, 
the  companion  veins  of  the  suprascapular  and  transversa  colli 
arteries.  These  veins  usually  unite  before  entering-  the 
subclavian;  but  occasionally  enter  by  separate  opening-s.      The 


THE  VENOUS  SYSTEM.  377 

external  jug-ular  vein,  which  sends  a  branch  to  the  cephalic, 
also  empties  into  the  subclavian.  The  manner  of  its  entrance 
will  be  described  later.  The  subclavian  then  receives  the 
companion  branches  from  the  thyroid  axis,  internal  mammary, 
and  vertebral  arteries,  and  terminates  behind  the  sterno- 
clavicular articulation  by  unitingf  with  the  internal  jug-ular  to 
form  one  of  the  innominate  veins. 

The  Veins  of  the  Head  and  Neck. 

The  Veiiis  of  the  Head  consist  of  a  set  of  channels  found  in 
the  cranium,  formed  by  divisions  in  the  dura  mater,  and  called 
"sinuses",  while  the  veins  of  the  neck  are  described  under  the 
name  of  "jug"ular"  veins  {Lt.  Jug-nluni — diminutive  of  jiigum, 
the  yoke — the  throat),  of  which,  however,  there  are  three:  the 
Internal,  External,  and  Anterior  Jug"ular.  In  addition  to 
these  jugular  veins  there  are  smaller  veins,  such  as  the  thyroid 
and  the  vertebral,  which  durino-  a  portion  of  their  course  are 
found  Ijnng-  in  the  neck.  Certain  veins  are  also  found  upon 
the  face,  which  aid  in  forming-  the  jug"ulars. 

The  Veins  of  the  Diploe. 

Ramifying  between  the  tables  of  the  bones  of  the  skull  are 
numerous  veins  called  diploetic.  They  take  the  name  of  the 
region  they  occupy  and  finally  converge  to  form  trunks  which 
open  either  into  the  sinuses  of  the  interior  or  the  veins  of  the 
exterior.  Connecting  the  sinuses  of  the  interior  with  the  veins 
of  the  exterior  of  the  head  are  several  veins  which  pass  through 
foramina  such  as  the  mastoid  and  parietal. 

The  Sinuses  of  the  Dura  Mater. 

Superior  Longitudinal  Inferior  Longitudinal 

Straight  Lateral 

Cavernous  Occipital 

Superior  Petrosal  Inferior  Petrosal 

These  Sinuses  are  formed  by  the  union  of  veins  found  in 
two  positions  in  the  cranium  :  one  set  called  the  veins  of  the 
Diphe  lying  between  the  two  tables  of  which  the  bones  of  the 
skull  are  composed,  while  the  other  set,  the  Cerebral   veins, 


378  DESCRIPTIVE  ANATOMY. 

are  found  ramifying-  over  the  surface  and  in  the  interior  of  the 
encephalon.  The  Cerebral  Veins  consist  of  two  sets,  super- 
ficial and  deep.  The  superficial  lie  upon  the  surface  of  the 
brain,  while  the  deep  cerebral  veins  lie  in  the  ventricular 
cavities  of  the  brain,  ultimately  uniting-  to  form  two  ventricu- 
lar veins,  the  Venae  Galeni,  which  leave  the  interior  of  the 
brain  throug-h  the  g-reat  transverse  fissure  and  terminate  in 
the  straig-ht  sinus. 

The  Snperior  Longitudinal  Sinus, 

The  Superior  Long-itudinal  Siruis  commences  at  the  fora- 
men caecum,  where  it  communicates  with  the  small  veins  of 
the  nasal  fossa.  The  g-roove  along  which  it  rnns  may  be  dis- 
covered on  the  dried  bones  as  occupying-  the  mid-line  of  the 
frontal  bone,  and  g-rooving-  equally  the  upper  border  of  the 
two  parietal  bones.  Leaving  these  b^nes,  it  appears  on  the 
occipital,  grooves  it  in  the  mid-line,  and  pisses  backward  to 
the  torcular  Herophili  by  the  side  of  the  anterior  occipital 
protuberance,  to  diverg-e  on  one  or  the  other  side  into  one  of 
the  lateral  sinuses.  This  sinus,  like  other  sinuses  of  the  dura 
mater,  is  not  strictly  speaking-  a  vein  :  it  is  the  spice  between 
two  layers  of  the  dura  ;  and  its  resemblance  to  a  vein  consists 
only  in  two  facts  ;  viz,  that  it  conveys  venous  blood,  and 
that  it  is  lined  internally  by  the  endothelial  coat,  which  all 
blood-vessels  contain.  As  it  passes  along-  the  g-roove,  this 
sinus  receives  the  superficial  cerebral  veins. 

The  Inferior  Longitudinal  Sinus. 

The  Inferior  Longitudinal  Sinus  is  a  small  sinus,  circular 
on  cross-section  (unlike  the  superior,  which  is  triang-ular  on 
cross-section).  It  commences  near  the  anterior  extremity  of 
the  falx  major,  follows  the  curvature  of  that  subdivision  of 
the  dura  miter,  and  passes  backward  to  the  junction  of  the 
falx  major  with  the  tentorium  cerebelli,  where  it  empties  into 
the  straig-ht  sinus. 

The  Straight  Sinus. 

The  Straight  Sinus  runs  in  the  triang-ular  interval  between 
the  falx  major  and  the  tentorium,  to    terminate    in   one  of  the 


THE  VENOUS  SYSTEM.  379 

lateral  sinuses.  Before  receiving*  the  inferior  longitudinal 
sinus,  the  straight  sinus  first  receives  the  venae  Galeni,  coming 
from  the  ventricles  of  the  brain. 

The  Occipital  Sinus. 

The  Occipital  Sinus  is  the  smallest  of  the  cranial  sinuses  ; 
it  commences  by  several  small  vein  around  the  foramen  magnum, 
and  is  situated  in  the  attached  marg-in  of  the  falx  cerebelli, 
communicating-  with  the  posterior  spinal  vein,  and  finally 
emptying-  into  the  torcular  Herophili. 

The  Cavernous  Sinuses. 

The  Cavernous  Sinuses  are  found  on  the  lateral  aspect  of 
the  body  of  the  sphenoid.  They  commence  in  front  by  receiving 
the  opthalmatic  veins  from  the  sphenoidal  fissure.  The 
opthalmic  veins,  following-  the  course  of  the  opthalmic  artery, 
pass  over  the  sphenoidal  fissure,  and  empty  into  the  cavernous 
sinuses.  These  in  turn,  winding-  along-  the  lateral  aspect  of 
the  body  of  the  sphenoid,  pass  to  the  junction  of  that  bone 
with  the  petrous  portion  of  the  temporal,  and  there  join  with 
the  petrosal  sinuses.  Stretching- across  between  the  cavernous 
sinuses  are  two  small  transverse  vessels,  which  surround  the 
pituitary  body,  one  in  front  and  the  other  behind.  These 
tog-ether  form  the  Circular  Sinus. 

After  the  cavernous  sinuses  have  received  the  superior 
petrosal  and  emptied  into  the  inferior  petrosal  sinus  on  the 
side  of  the  basilar  process  of  the  occipital  bone,  they  are  united 
by  a  small  vein,  extending-  between  the  two,  which  is  called 
the   Transverse  Sinus. 

The  Superior  Petrosal  Sinus. 

The  Superior  Petrosal  Sinus  is  situated  on  the  upper  bor- 
der of  the  petrous  portion  of  the  temporal.  Its  inner  extremity 
is  connected  with  the  cavernous  sinus,  while  its  outer  is 
connected  with  the  lateral  sinus,  just  as  that  sinus  reaches  the 
inner  face  of  the  mastoid  portion  of  the  temporal,  and  receives 
the  mastoid  veins. 

The  Inferior  Petrosal  Sinus. 

The  Jnfcrior  Petrosal  Sinus  occupies  the  groove  between 


380  DESCRIPTIVE  ANATOMY. 

the  posterior  border  of  the  petrous  portion  of  the  temporal  and 
the  inner  half  of  the  lower  border  of  the  occipital.  It  receives 
the  cavernous  sinus  in  front;  and  terminates  behind  by  uniting- 
with  the  lateral  sinus. 

The  Lateral  Sinuses. 

The  Lateral  Simtses  commence  at  the  torcular  Herophili, 
where  the  long-itudinal  sinus  empties.  The  torcular  is  never 
situated  on  the  mid-line  of  the  body;  but  to  one  or  the  other 
side,  more  frequently  to  the  rig^ht.  The  blood  from  the 
superior  long-itudinal  sinus  pours  into  the  lateral  sinus  of  the 
rio-ht  side,  while  the  current  of  blood  from  the  occipital  and 
straig"ht  sinuses  usually  passes  into  the  opposite  lateral  sinus. 

The  lateral  sinus  of  each  side  arches  outward  along  the 
anterior  face  of  the  occipital  bone;  but  leaves  that  bone  to 
appear  momentarily  on  the  postero-inferior  asg-le  of  the  parietal. 
Leaving-  the  parietal,  it  passes  downward  and  inward  in  a 
curved  direction  across  the  internal  face  of  the  mastoid  portion 
of  the  temporal,  forming-  a  deep  depression  in  this  bone,  the 
fossa  sigmoidea  and  finally  at  the  posterior  extremity  of  the 
jugular  (the  foramen  lacerum  posterius),  it  unites  wnth  the 
inferior  petrosal  sinus  to  form  the  internal  jugular  vein. 

It  will  be  seen,  therefore,  that  the  right  internal  jugular 
conveys  the  blood  received  from  the  superior  lougitudinal  sinus, 
which,  in  its  turn,  receives  the  superficial  cerebral  veins,  w^hile 
the  left  internal  jugular  conveys  most  of  the  blood  carried  by 
the  venaj  Galeni,  and  from  this  by  the  straight  sinus,  into  the 
left  lateral  sinus.  The  veins  of  the  base  of  the  brain  are  about 
equally  distributed  by  means  of  the  petrosal,  transverse  and 
circular  sinuses  into  the  corresponding  jugular  veins. 

It  must  never  be  forgotten  that  the  veins  of  the  diploe  com- 
municate with  the  sinuses  of  the  dura  mater  on  the  one  hand, 
while  on  the  other  they  communicate  with  the  superficial  veins 
of  the  cranium.  These  communicating  veins  are  described  as 
emissary  veins,  so  that  any  infection  of  the  tissues  occupying 
the  surface  of  the  skull  may  readily  pass  along  the  course  of 
the  emissary  veins  into  the  interior  of  the  skull,  and  so  estab- 
lish an  inflammation  of  the  brain  itself. 


THE  VENOUS  SYSTEM.  381 

The  Internal  Jugular. 

The  Liternaljiignlar  F^/;/, formed, as  above  described,  by  the 
union  of  the  inferior  petrosal  with  the  lateral  sinus,  is  a  larg-ely 
dilated  aperture  at  the  base  of  the  cranium  ;  but  it  quickly 
contracts  to  about  twice  the  size  of  the  internal  carotid  artery. 
At  its  origin  it  lies  immediately  behind  the  internal  carotid  ar- 
ter}^  with  the  twelfth,  or  hypo-glossal,  nerve  behind  it,  and 
the  ninth,  tenth,  and  eleventh  cranial  nerves  emerging-  in  the 
interval  between  itself  and  the  internal  carotid.  It  then  passes 
downward  as  an  external  relation  of  the  internal  carotid  to  the 
point  at  which  that  vessel  is  derived  from  the  common  carotid 
artery  ;  then  becomes  a  relation  of  the  common  carotid  artery, 
and  maintains  that  relation  to  the  origin  of  that  vessel  behind 
the  sterno-clavicular  articulation,  where  it  terminates  by  join- 
ing the  subclavian  vein  to  form  the  innominate  vein  of  thatside. 
In  its  course  down  the  neck,  the  glosso-pharyngeal  and  hypo- 
glossal nerves  pass  forward  between  the  artery  and  the  vein, 
to  cross  the  front  of  the  artery  and  cease  to  be  relations  of  the 
vein.  The  eleventh,  or  spinal  accessory,  nerve  passes  behind 
the  vein  near  the  upper  portion  of  its  course  ;  but  the  tenth 
continues  an  internal  relation  of  the  internal  jugular  through- 
out the  entire  course  of  that  vein. 

Its  tributaries  are  the  Facial,  Lingual,  Pharyngeal,  Super- 
ior and  Middle  Thyroid  Veins. 

The  Vertebral  Veins. 

The  Vertebral  Veins  commence  by  tributaries  at  the  upper 
part  of  the  back  of  the  neck,  pass  downward  in  the  foramina 
of  the  transverse  processes,  which  transmit  the  vertebral 
artery  ;  and  the  two  satellites  unite,  one  passing  through  the 
sixth  and  the  other  through  the  seventh  transverse  process, 
to  form  a  single  vein,  which  empties  into  the  innominate  vein 
of  the  corresponding  side. 

The  Veins  of  the  Face. 

The  Veijis  of  the  /^«6'6' consist  of  numerous  branches,  which 
correspond  to  the  arteries  of  the  face.     Of  these,  the  Supra- 


382  DESCRIPTIVE  ANATOMY. 

orbital  commencing-  on  the  forehead,  communicates  with  the 
temporal  vein,  and  joins  the  frontal  to  form  the  Facial  vein. 
This,  after  receiving*  the  Nasal,  Superior  Labial,  Transverse 
Facial,  and  Inferior  Labial,  passes  over  the  lower  border  of 
the  jaw,  about  an  inch  in  front  of  the  angle,  or  opposite  the 
internal  border  of  the  masseter  muscle,  receives  a  communi- 
cation from  the  tempero-maxillary  vein,  and  empties  into  the 

internal  jug-ular. 

The  Temporal  Veins. 

The  Tenifioral  Veins  commence  on  the  lateral  aspect  of  the 
skull  by  numerous  tributaries,  pass  downward  in  an  interval 
between  the  internal  auditory  meatus  and  the  tempero-maxil- 
lary articulation,  run  into  the  substance  of  the  parotid  g-land, 
and  receive  the  internal  maxillary  vein,  made  up  of  tributa- 
ries accompanying"  branches  of  the  internal  maxillary  artery, 
and  behind  the  neck  of  the  condyle  of  the  lower  jaw  forms  the 
tempero-maxillary  vein. 

This  vein  divides  into  two  branches,  one  of  which  has  been 
already  alluded  to  as  uniting*  with  the  facial  vein  to  empty 
into  the  internal  jug-ular,  while  the  other  unites  with  the  pos- 
terior auricular  to  become  the  external  jug"ular  vein. 

The  External  Jugular. 

The  External  Jug-ular  Vein,  commencing*  in  the  substance 
of  the  parotid  g-land,  receiving-  the  g-reater  portion  of  the  blood 
from  the  exterior  of  the  cranium  and  the  deep  parts  of  the  face, 
runs  down  the  neck  in  the  direction  of  the  fibres  of  the  platysma 
myoides  muscle,  which  covers  it.  It  runs  nearly  parallel 
w^ith  the  posterior  border  of  the  sterno-cleido-mastoid  muscle 
until  it  reaches  a  point  just  above  the  clavicle,  where  it 
chang-es  its  direction,  and  passing-  downward  and  inward, 
empties  into  the  subclavian  vein. 

The  Innominate  Veins. 

The  Innominate  Veins  of  the  two  sides  differ  in  direction, 
though  but  little  in  formation. 

On  the  right  side  the  innominate  vein  has  already  been 
described  as  formed  behind  the  rig-ht  sterno-clavicular  articu- 


THE  VENOUS  SYSTEM.  383 

lation  by  the  union  of  the  subclavian  and  internal  jugular  veins. 
0)1  the  left  side  the  vein  is  formed  in  the  same  way  ;  but 
usually  the  internal  jugular  lies  to  the  outer  front  aspect  of 
the  left  subclavian  arter}',  instead  of  crossing  directly  over 
the  front,  as  is  the  case  on  the  right  side. 

The  innominate  vein  on  the  right  passes  downward  and  in- 
ward, parallel  with  and  anterior  to  the  innominate  artery, 
and  a  little  to  the  right  side  of  that  vessel.  On  the  left,  the 
innominate  vein,  also  called  the  Great  Transverse  Vein  of  the 
Neck,  crosses  successively  the  thoracic  portions  of  the  left 
subclavian  and  left  common  carotid  arteries  and  the  arteria 
innominata,  and  lying  above  and  on  a  plane  anterior  to  the 
transverse  aorta.  At  the  commencement  of  the  transverse 
aorta  the  two  innominate  veins  unite  to  form  the  Superior  Vena 
Cava. 

The  Superior  Vena  Cava. 

The  Superior  Vena  Cava  descends  anterior  and  external  to 
the  ascending  aorta,  pierces  the  fibres  of  the  pericardium,  and 
enters  the  venous,  or  right,  auricle  of  the  heart  on  the 
upper  front  aspect  of  that  organ. 

Besides  these  veins  there  are  several  smaller  veins  which 
are  found  mainly  in  the  thoracic  cavity  and  lower  portion  of 
the  neck. 

Of  these,  the  satellite  veins  of  the  Internal  Mammary  Artery 
empty  into  the  corresponding  innominate  vein. 

The  Inferior  Thyroid  Veins,  accompanying  the  artery  of 
the  same  name,  pass  likewise  into  the  corresponding  innominate 
veins. 

The  Superior  Intercostal  Veins,  returning  the  blood  from 
the  upper  intercostal  spaces,  except  the  first,  empty,  the  right 
one  into  the  vena  azygos  major,  the  left  usuall}"  into  the  left 
innominate  vein. 

The  A2yfi'os  Vei?is  connect  the  superior  and  inferior  venae 
cava,'.  They  are  two  in  number,  the  right  azygos,  or  vena 
azygos  major,  and  the  left  azygos,  or  vena  azygos  minor. 

The  Vena  Azygos  Major. 

^):\{t  Azygos  ^^/tt/V^r  commences  in  the  abdominal  cavity  oppo- 


384  DESCRIPTIVE  ANATOMY. 

site  the  first  or  second  lumbar  vertebra,  sometimes  from  the 
first  lumbar  vein,  sometimes  by  a  branch  from  the  renal  vein. 
It  enters  the  thorax  throug-h  the  aortic  opening-  of  the  diaph- 
ragm; and  receiving-  branches  from  the  lower  six  intercostal 
spaces,  finally  terminates  by  crossing  the  vertebral  column 
opposite  the  sixth  dorsal  vertebra  behind  the  thoracic  aorta, 
and  empties  into  the  superior  vena  cava  just  before  that  vessel 
passes  into  the  heart. 

The  Vena  Azyg-os  Minor. 

Just  before  the  azygos  major  crosses  the  vertebral  column 
it  is  joined  by  the  Vejia  Azyg-os  Minor,  which  conveys  the 
blood  from  the  intercostal  spaces  between  the  superior  azygos, 
already  described  as  the  Left  Superior  Intercostal,  and  the 
highest  branches  entering  into  the  azygos  minor.  At  its  lower 
extremity  this  vessel  frequently  communicates  with  the  inferior 
vena  cava,  and  thus  directly  establishes  a  communication  be- 
tween the  superior  and  inferior  venae  cavae.  Occasionally, 
however,  the  communication  consists  entirely  of  a  brancH  from 
the  renal  vein,  w^hich  in  its  turn  empties  into  the  inferior  vena 
cava,  and  thus  indirectly  establishes  this  communication. 

The  Spinal  Veins. 

The  spinal  veins  consist  of  three  sets,  as  follows  : 

Dorsal  Spinal  Veins. 

The  dorsal  spinal  veins  are  numerous  veins  forming  a  net- 
work on  the  exterior  of  the  vertebrae. 

Meningo-Rachidian  Veins. 

The  meningo-rachidian  are  four  veins  perpendicular  in  di- 
rection, which  lie  within  the  spinal  canal  between  the  bone 
and  dura  mater,  two  in  front  and  two  behind. 

Medulli-Spinal  Veins. 

The  meduUi-spinal  are  numerous  veins  ramifying  beneath 
the  arachnoid  membrane  of  the  spinal  cord. 


THE  VENOUS  SYSTEM.  385 

The  Cardiac  Veins. 

The  veins  of  the  heart  are  two,  as  follows  : 

The  Great  Cardiac  Vein. 

The  great  cardiac  vein  ascends  in  the  anterior  ventricular 
g-roove,  winds  around  the  left  auriculo-ventricular  g-roove  and 
opens  into  the  rig-ht  auricle.  The  last  inch  of  its  course  is 
known  as  the  coronary  sinus. 

The  Posterior  Cardiac  Vein. 

The  posterior  cardiac  vein  is  small  and  ascends  in  the  pos- 
terior ventricular  groove  to  open  into  the  g^reat  cardiac  vein. 

Des  Anat — 25 


386  DESCRIPTIVE  ANATOMY. 


THE  LYMPHATIC  SYSTEM. 

The  lymphatic  system  consists  of  numerous  small  vessels 
ramifyinof  in  nearly  every  tissue  of  the  body,  and  of  small, 
reddish,  pea-like  bodies  called  h^mphatic  g^lands,  found  at 
intervals  along-  the  lymphatic  vessels.  The  lymphatic  vessels 
are  intended  for  the  most  part  to  remove  from  the  tissues  the 
detritus  of  assimilation,  consisting-  mainly  of  unexpended 
plasma  ;  consequently  the  course  of  their  circulation  is  from 
the  circumference  towards  the  centre,  and  in  their  route  they 
will  be  found  to  accompany  the  veins. 

Wherever  they  are  found  the  lymphatics  consist  of  two  sets, 
superficial  and  deep.  In  the  extremities  the  superficial  set 
is  found  just  benseth  the  skin  ;  the  deep  in  and  among-  the 
muscles.  In  the  viscera  the  superficial  set  ramifies  on  the 
surface,  while  the  deep  is  found  in  the  structure.  The  g-reater 
portion  of  the  lymphatics  of  the  body  converg-e  to  form  one 
larg-e  vessel,  the  thoracic  duct,  which  empties  into  the  venous 
current  near  the  heart. 

Thoracic  Duct. 

The  thoracic  duct  beg-ins  on  the  front  of  the  body  of  the 
second  lumbar  vertebra  by  a  considerable  dilatation  called 
receptaculum  chyli,  which,  narro\ving-  to  a  tube  the  size  of  a 
g-oose  quill,  ascends  the  front  of  the  vertebral  column  behind 
the  descending-  aorta,  passes  throug-h  the  aortic  opening-  of 
the  diaphrag-m  and  continues  upward  as  hig-h  as  the  fourth 
dorsal  vertebra,  w^here  it  inclines  to  the  left  and  continues 
thence  an  oblique  ascent  behind  the  arch  of  the  aorta  to  a 
point  on  a  level  with  the  seventh  cervical  vertebra,  where  it 
arches  forward  and  downward  and  opens  into  the  commence- 
ment of  the  left  vena  innominata.  Opening  into  the  commence- 
ment of  the  rig-ht  vena  innominata  is  another  and  much  smaller 
lymphatic  duct  (ductus  lymphaticus  dexter)  which  conveys 
lymph  furnished  it  by  the  right  upper  extremity  and  rig-ht 
side  of  the  head  and  neck. 


THE  LYMPHATIC  SYSTEM.  387 


Lymphatics  of  the  Lower  Extremity. 

The  superficial  lymphatics  of  the  lower  extremity  are  found 
crowding"  upward  in  immense  numbers  along-  the  course  of 
the  saphenous  veins  and,  reaching-  the  saphenous  opening-  in 
the  fascia  lata,  where  the  vein  terminates  near  Poupart's  lig-- 
ament,  they  then  pass  throug-h  a  set  of  lymphatic  g-lands. 
The  deep  lymphatic  vessels  accompany  the  deep  veins  upward 
to  the  g-roin,  where  they  are  connected  with  a  set  of  g-lands, 
lying-  beneath  the  fascia  lata  and  superficial  muscles,  called 
the  deep  lymphatic  g-lands  of  the  g-roin.  Along-  the  course  of 
these  vessels  are  found  a  few  g-lands,  some  in  the  popliteal 
space  and  one  on  the  front  of  the  interosseous  membrane  of 
the  leg-.  The  lymphatic  vessels  from  the  external  organs  of 
g-eneration  and  from  the  abdominal  parietes  can  be  traced  to 
a  third  set  of  g-lands,  which  form  a  chain  along-  Poupart's 
ligament,  lying-  superficial  and  above  the  g-lands  around  the 
saphenous  opening-. 

All  these  vessels  pass  beneath  Poupart's  lig-ament  to  become 
the  external  iliac  lymphatics  which  accompany  the  external 
iliac  vessels  and  unite  with  the  internal  iliac  lymphatics  to  form 
the  common  iliac  lymphatics,  which  accompany  the  common 
iliac  vessels  and  unite  with  those  of  the  opposite  side  to  form 
the  lumbar  lymphatics.  Scattered  at  intervals  along-  these 
vessels  from  Poupart's  lig-ament  are  lymphatic  g-lands.  The 
lumbar  lymphatics  ascend  along-  the  aorta,  constantly  increas- 
ing in  size  by  accessions  from  the  abdominal  viscera,  and 
having-  passed  throug-h  numerous  g-lands,  and  lessened  in 
number  as  they  increased  in  size,  they  eventually  open  into  the 
receptaculum  chyli,  which  is  so  named  from  the  fact  that  the 
lymphatics  which  it  receives  from  the  small  intestine  are, 
during  the  process  of  dig-estion,  filled  with  chyle. 

The  Lymphatics  of  the  Upper  Extremity. 

The  lymphatics  of  the  upper  extremity,  like  those  of  the 
lower,  consist  of  a  superficial  and  a  deep  set.  The  superficial 
ascend  in  company  with  the  superficial  veins   and    the  deep 


388  DESCRIPTIVE  ANATOMY. 

accompany  the  deep  veins,  both  converg-ing-  to  the  arm  pit 
where  there  are  some  twelve  or  fifteen  lymphatic  glands. 
Besides  the  vessels  from  the  upper  extremity  these  g-lands  also 
receive  those  from  the  chest  wall  and  mammary  g-land.  A  few 
g-lands  are  found  along-  the  course  of  the  lymphatics  before 
they  reach  the  axilla,  some  at  the  elbow  and  some  along-  the 
brachial  vessels  ;  these,  however,  are  small  and  unimportant. 
From  the  axillary  g-lands  the  vessels  proceed  along-  the  course 
of  the  subclavian  vein,  opening  on  the  left  side  into  the  termi- 
nation of  the  thoracic  duct  and  on  the  right  into  the  ductus 
lymphaticus  dexter. 

Lymphatics  of  the  Head  and  Neck. 

The  lymphatics  of  the  head  and  neck  consist  of  vessels 
which  have  come  from  the  exterior  of  the  head  and  others 
which  have  converged  from  veins  supplying-  the  internal  and 
external  jug-ular  veins,  no  lymphatics,  however,  being-  found 
in  the  substance  of  the  brain. 

These  vessels  descend  along  the  external,  and  especially 
the  internal,  jugular  veins  and  on  the  right  side  open  into  the 
ductus  lymphaticus  dexter  while  on  the  left  they  join  the 
thoracic  duct. 

The  Lymphatics  of  the  Thorax. 

The  lymphatics  accompanying-  the  intercostal  vessels  open 
into  the  thoracic  duct.  Those  from  the  right  lung-,  some  portion 
of  the  thoracic  parietes,  diaphrag-m  and  even  some  portion  of 
the  upper  surface  of  the  liver  and  the  short  border  of  the  heart 
seek  the  ductus  lymphaticus  dexter  ;  while  those  from  the  left 
lung-,  left  side  of  the  thorax  and  most  of  the  heart  join  the 
thoracic  duct.  The  vessels  from  the  lung-s  pass  through  a 
set  of  glands  situated  around  the  bifurcation  of  the  trachea 
called  the  bronchial  glands. 


THE  CENTRAL  NERVOUS  SYSTEM.  389 


THE  CENTRAL  NERVOUS  SYSTEM. 

Cerebro- Spinal  Centres. 

The  chain  of  nervous  centres  known  as  the  Cerebrospinal 
axis  is  divided  into  two  portions,  one  contained  in  the  spinal 
canal,  and  called  the  spinal  cord,  or  Medulla  Spinalis  (L.  Me- 
dins,  middle),  the  other  contained  in  the  cranium  and  called 
the  Brain,  or  Encephalon,  the  latter  name  including  the  brain 
and  its  membranes.  Enveloping  each  of  these  portions  and 
lining  its  containing  cavity  are  three  membranes,  lying  one 
within  the  other,  called  the  Investing- Membranes^  or  Meninges. 

The  Membranes  of  the  Brain. 

The  membranes  of  the  Brain  are  the   Dura  Mater  (L.  Hard 

mother),   lying  next  to  the  cranial   wall ;  the  Pia  Mater   (L. 

Delicate  mother),  lying  next  to  the  brain  ;  and  the  Arachnoid 

between  the  two. 

The  Dura  Mater. 

The  Dura  Mater  is  a  grayish  white,  strong,  fibrous  mem- 
brane which  lines  the  inner  surface  of  the  cranial  wall,  adher- 
ing closely  to  the  bone,  and  supplying  the  place  of  an  internal 
periosteum.  Its  internal  surface  is  glistening  and  smooth 
because  lined  by  the  arachnoid,  which  performs  the  functions 
of  a  serous  membrane.  Besides  lining  the  interior  of  the  cra- 
nial cavity,  the  dura  mater  gives  off  septa,  which  passing 
between  the  different  portions  of  the  brain,  serve  to  separate 
them  from  one  another  and  to  support  the  brain  in  its  position, 
besides  carrying  blood-vessels  which  receive  and  return  the 
circulation  from  the  interior  of  the  cavity.  These  processes 
are  three  in  number  :  the  Falx  Major,  or  Falx  Cerebri,  the 
Tentorium  Cerebelli,  and  the  Falx  Minor,  or  Falx  Cerebelli. 
The  Falx  Major  (L.  Falx,^  scythe),  or  Falx  Cerebri,  is  a 
sickle-shaped  process  which  lies  in  the  great  longitudinal 
fissure  of  the  brain.  It  is  attached  in  front  to  the  crista  galli 
and  extends  along  the  mid-line  to  the  anterior  occipital  pro- 
tuberance, and  is  attached  to  the  superior  surface  of  the 
tentorium  along  its  middle  line.     Along  its  attachment  to  the 


390  DESCRIPTIVE  ANATOMY. 

cranium,  the  Falx  major  divides  into  two  layers,  which  are 
attached  to  the  marg-ins  of  the  g-roove  found  on  the  frontal, 
parietal,  and  occipital  bones.  Between  these  two  layers  is  a 
triangular  space,  which  lodg^es  one  of  the  important  sinuses, 
the  siifierior  long-itudiiial  sinus.  The  concave  lower  margin 
is  hollowed  out  into  a  small  canal,  circular  on  cross  section, 
which  extends  from  the  foramen  caecum  to  the  attachment  of 
the  falx  major  to  the  tentorium.  This  is  called  the  inferior 
longitudinal  sinus. 

The  Tentorium  (L.  Tendere,  to  stretch)  commences  at  the 
posterior  occipital  protuberance,  and  passing-  transversely 
forward,  extends  into  the  g-reat  transverse  fissure  of  Bichat 
separating-  the  cerebrum  from  the  cerebellum,  serving-  to  sup- 
port the  posterior  lobes  of  the  cerebrum  and  at  the  same  time 
to  bind  the  cerebellum  in  the  cerebellar  fosss.  Along-  its 
upper  surface  from  before  backwards  is  attached  the  posterior 
extremity  of  the  falx  major.  Its  posterior  border,  divided  like 
the  falx  major  into  two  layers,  is  attached  along-  the  marg-in 
of  the  lateral  limbs  of  the  occipital  cross  ;  and  leaving-  this 
bone,  passes  forward  on  the  superior  border  of  the  petrous 
portion  of  the  temporal  bone,  at  the  apex  of  which  it  is  joined 
by  the  concave  free  anterior  border.  This  anterior  border 
presents  a  horseshoe-shaped  appearance,  and  when  the  two 
borders,  anterior  and  posterior,  meet  with  one  another,  they 
cross,  so  that  the  free  border  continues  forward  to  be  attached 
to  the  anterior  clinoid  process,  while  the  attached  border 
reaches  the  posterior  clinoid  process.  Between  these  attach- 
ments is  left  an  opening-  through  which  is  transmitted  the 
mid-brain.  At  the  attachment  of  the  posterior  border  is  a 
sinus,  a  continuation  of  the  great  longitudinal  sinus  on  one 
side,  forming  the  lateral  sinus.  Where  the  tentorium  is 
attached  to  the  upper  border  of  the  petrous  portion  of  the 
temporal  is  another  sinus,  the  superior  petrosal ;  and  where 
the  falx  major  is  attached  on  the  superior  surface  of  the  ten- 
torium is  found  a  third  sinus,  the  straig-Jit  sinus  passing  back- 
ward to  the  torcular  Herophili. 

The  Falx  Cerehelli  is  a  small  narrow  process  of  the  dura, 
which    extends    from    the    margin    of    the    foramen    magnum 


THE  CENTRAL  NERVOUS  SYSTEM.  391 

Upward  to  the  under  surface  of  the  tentorium  to  the  posterior 
part  of  which  it  is  attached,  at  the  anterior  occipital  protuber- 
ance. It  projects  between  the  two  lobes  of  the  cerebellum, 
and  serves  to  separate  them  from  one  another. 

The   Arachnoid. 

The  Arachnoid^  like  all  serous  membranes,  presents  a 
closed  sac,  one  of  its  layers  lining-  the  inner  surface  of  the 
dura,  and  being-  called  the  parietal  layer,  while  the  other 
invests  the  brain,  from  which  it  is  separated  by  the  pia,  and 
is  called  the  visceral  layer.  It  does  not  dip  into  the  sulci  of 
the  brain  ;  but  leaps  from  convolution  to  convolution,  so  that 
a  space  is  interposed  at  various  portions  of  the  brain  between 
the  arachnoid  and  the  pia  mater.  This  space  has  received  the 
hybrid  name  of  Sub-Arach)ioidean.  It-can  be  easily  demon- 
strated at  some  portions  of  the  brain,  while  at  others  it  is 
scarcely  perceptible.  On  the  inferior  surface  of  the  brain, 
stretching-  between  the  two  peduncles  of  the  cerebrum,  and 
covering  the  inter-peduncular  space,  a  considerable  distance 
exists  between  the  pia  and  the  arachnoid  ;  and  ag-ain  in  the 
great  transverse  fissure  of  Bichat  the  space  can  be  easily  made 
apparent. 

The  Pia  Mater. 

The  P/«  J/«/6'r  is  an  extremely  thin  and  very  vascular  mem- 
brane, consisting  almost  entirely  of  small  interlacing-  bloodves- 
sels, held  tog-ether  by  layers  of  connective  tissue.  It  covers  the 
entire  surface  of  the  brain  ;  and  not  only  does  this,  but  dips 
into  every  sulcus  and  every  depression  of  the  brain.  Thus,  it 
passes  throug-h  the  g-reat  transverse  fissure  of  Bichat,  covering- 
not  only  the  cerebellum  and  the  under  surface  of  the  cerebrum; 
but  continuing-  through  this  fissure,  it  passes  even  into  the 
interior  of  the  brain  itself,  so  that  prolong-ations  of  the  pia  are 
found  in  the  ventricles,  in  the  interior  of  the  hemispheres, 
and  connecting  with  the  blood  vessels  which  perforate  from 
the  base  of  the  brain  and  supply  the  structures  in  the  interior 
of  each  hemisphere.  It  serves  also  in  one  portion  of  the  brain 
to  form  the  roof  of  one  of  the  ventricles.  An  examination  of 
the  brain  with  its  frec^uent  elevations  and  depressions  forming- 


392  DESCRIPTIVE  ANATOMY. 

the  convolutions  and  sulci  would  show  that  if  this  membrane 
were  stripped  off,  its  area  would  be  enormously  g-reater  than 
the  apparent  area  of  the  brain  itself.  E^very  sulcus  into  which 
the  membrane  dips  forms  a  corresponding- fold,  so  that  it  bears 
a  close  resemblance  in  its  folds  to  a  dress  or  other  garment 
which  has  been  taken  out  of  a  trunk. 

The  Brain. 

The  Ence-phalon  is  divided  into  four  parts:  the  Cerebrum, 
the  Cerebellum,  the  Pons  Varolii,  and  the  Medulla  Oblongata, 
the  Pons  and  its  appendages  being  frequently  described  as 
the  iJiid-brain. 

The  zveight  of  the  entire  brain  varies  with  the  period  of 
life,  with  the  sex  of  the  individual,  with  the  cause  of  death, 
the  period  after  death  at  which  the  weight  is  taken,  and  with 
various  other  circumstances.  The  average  w^eight  is  about 
forty-eight  ounces  for  the  male,  and  about  forty-four  or  forty- 
five  for  the  female  adult.  The  intellectuality  of  the 
individual  bears  scarcely  any  relation  to  the  weight  of  the 
brain,  some  of  the  heaviest  brains  having  been  those  of  people 
by  no  means  distinguished  for  ability,  while  comparatively 
small  brains  have  been  found  in  people  of  a  high  order  of 
intelligence.  The  intellectuality  varies  more  with  the  variety 
and  number  of  the  convolutions,  and  consequently  with  the 
amount  of  "gray  matter,"  than  it  does  with  the  actual  bulk  of 
the  brain. 

The  Cerebrum  is  seven  or  eight  times  the  size  of  the  rest 
of  the  brain,  presenting  an  uneven,  convoluted  surface.  When 
closely  examined  these  convolutions  are  seen  to  be  dissimilar 
on  the  two  sides  of  the  brain,  nor  do  we  ever  find  any  two 
brains  with  precisely  the  same  convolutions.  Certain  depres- 
sions which  separate  these  convolutions  from  one  another, 
from  the  fact  that  they  appear  at  an  early  stage  of  foetal  life, 
are  called  "primary  fissures,"  and  from  these  primary  fissures 
we  get  the  great  subdivisions  of  the  cerebrum.  These  pri- 
mary fissures  are  the  Great  Long-itiidiiial  Fissure^  the  Great 
Transverse  Fissure  of  Bichat,  the  Fissure  of  Sylviiis,  the 
Fissure  of  Rolando,  and  the  Parieto-occipital  Fissure.     The 


THE  CENTRAL  NERVOUS  SYSTEM.  393 

_g-)-eat  lo)i§iti(di)ial  Jissitrc  serves  to  separate  the  two  lobes  of 
the  cerebrum  ;  the  trcDisvcrsc  /iissi(7'c  of  Bichat  to  separate 
the  cerebrum  from  the  cerebellum  ;  the^'^^^rr^^  of  Sylvius  to 
separate  the  frontal  from  the  tempero-sphenoldal,  and  by  its 
horizontal  limb,  the  parietal  from  the  tempero-sphenoidal  ; 
the  fissure  of  Rolando  to  separate  the  frontal  from  the  parie- 
tal ;  while  the  parieto-occipital  of  course  separates  the  parietal 
and  occipital  lobes. 

The  Convolutions  of  the  Cerebrum. 

In  studying-  the  convolutions  of  the  cerebrum  we  beg-in 
with  the  five  principal,  or  primary,   fissures. 

The  Great  Lo)igitudinal  Fissure  commences  on  the  base  of 
the  brain,  extends  upward  between  the  two  hemispheres,  turns 
backward  toward  the  posterior  extremity,  and  cutting-  between 
the  two  hemispheres  behind,  separates  them  from  one  another. 
It  will  therefore  be  seen  that  the  two  hemispheres  of  the 
cerebrum  are  united  in  the  middle,  but  are  separated  in  front 
and  behind.  The  bond  of  union  between  them,  the  corpus 
callosum,  extends  further  in  front  than  behind  and  is  thicker 
there  than  in  front. 

The  Fissure  of  Sylvius.  Commencing-  on  the  base  of  the 
brain  near  the  g-reat  long-itudinal  fissure,  or,  more  correctly, 
at  the  anterior  perforated  spot,  is  the  fissure  of  Sylvius.  It 
is  first  directed  outward,  forming-  a  means  of  separation 
between  the  frontal  and  tempero-sphenoidal  lobes.  On  leaving- 
the  base  of  the  brain  to  appear  on  the  outer  surface  of  the 
hemisphere,  chang-es  its  direction  and  passes  upward  and 
backward,  forming-  what  is  called  the  horizontal  limb  of  the 
fissure  of  Sylvius,  which  separates  the  tempero-sphenoidal 
below  from  the  parietal  above.  The  liorizoiital  li))ib  of  the 
fissure  of  Silvius  extends  backward  as  far  as  the  commence- 
ment of  the  occipital  lobe,  or  the  junction  of  about  the  posterior 
one-fifth  with  the  anterior  four-fifths  of  the  cerebrum.  Just 
as  the  main  fissure  reaches  the  outer  surface  of  the  hemisphere, 
the  vertical  limb  is  g-iven  off,  which  ascends  in  the  convolutions 
of  the  frontal  lobe,  forming-  in  this  situation  an  overhang-ing- 
appearance,  which  is  described  as  the  Operculum  {L.  Operire, 
to  cover.) 


394  DESCRIPTIVE  ANATOMY. 

The  Fissure  of  Rolando  is  situated  about  the  middle  of  the 
outer  surface  of  either  hemisphere.  It  beg-ins  near  the  lono-i- 
tudinal  fissure  and  runs  first  downward  and  forward  about 
one-half  of  its  course.  It  then  makes  an  abrupt  knee-like  bend; 
and  passing-  nearly  vertically  downward,  terminates  near  the' 
division  of  the  fissure  of  Sylvius  into  its  horizontal  and  its 
vertical  limbs. 

The  Parieto- occipital  Fissure  is  but  slig^htly  seen  on  the 
outer  surface  of  the  hemisphere,  the  main  portion  of  the  fissure 
lying-  on  the  inner  face.  It  commences  beneath  the  g"yrus 
fornicatus  opposite  the  splenium  of  the  corpus  callosum  ;  and 
passes  upward  and  forw-ard  to  emerge  on  the  outer  surface  of 
the  hemisphere,  just  in  the  g-reat  longitudinal  fissure. 

By  these  primary  fissures  the  hemisphere  is  divided  into  five 
lobes,  frontal,  parietal,  occipital,  tempero-sphenoidal,  and  cen- 
tral, or  island  of  Reil. 

The  Frontal  Lobe  is  all  of  that  portion  of  the  brain  situated 
in  front  of  the  fissure  of  Rolando,  hence  it  would  be  bounded 
above  by  the  g-reat  long-itudinal  fissure,  on  the  outer  surface, 
behind,  by  the  fissure  of  Rolando,  on  the  lower  surface,  behind, 
by  the  main  portion  of  the  fissure  of  Sylvius.  It  should  be 
noted  that  the  inner  face  of  the  various  lobes  of  each  hemi- 
sphere is  not  described  along-  with  the  external  and  inferior 
faces,  the  reason  being-  that  the  convolutions  and  fissures  on 
the  internal  face  do  not  confine  themselves  to  lobes,  but  extend 
in  many  cases  throug-hout  the  entire  leng-th  of  the  hemisphere. 

The  Parietal  Lobe  is  bounded  above  by  the  great  longitudi- 
nal fissure,  in  front  by  the  fissure  of  Rolando,  below  by  the 
horizontal  limb  of  the  fissure  of  Sylvius,  and  a  line  connecting 
this  with  the  lower  end  of  the  superior  occipital  sulcus,  and 
behind  by  the  parieto-occipital  fissure  and  a  line  drawn  in 
continuation  of  that  sulcus.  This  fissure  lies  mainly  on  the 
inner  face  of  the  hemisphere,  so  that  on  the  outer  face,  the 
convolutions  of  the  parietal  become  continuous  with  those  of 
the  occipital  lobe. 

The  Occipital  Lobe  is  cut  off  on  its  inner  face  by -the  Pari- 
eto-occipital fissure  from  the  parietal  lobe,  this  fissure  being- 
its  anterior  boundary.     Above  it  is  bounded  by  the  longitudi- 


THE  CENTRAL  NERVOUS  SYSTEM.  395 

nal  fissure,  while  below  its  convolutions  run  into  the  convolu- 
tions of  the  parietal  and  tempero-sphenoidal  lobes,  there  being- 
no  fissure  to  form  a  separation. 

The  Temi)oro-sj)henoidal  Lobe  is  that  portion  which  lies  in 
the  middle  fossa  of  the  skull.  On  the  inferior  surface  of  the 
base  of  the  brain  it  is  bounded  in  front  by  the  fissure  of  Syl- 
vius ;  externally,  it  is  bounded  above  by  the  horizontal  portion 
of  the  fissure  of  Sylvius ;  while  posteriorly  it  blends  around 
this  horizontal  limb  of  the  fissure  of  Sylvius  with  the  occipital 
and  parietal  lobes. 

The  Island  of  Rcil  is  a  cluster  of  five  or  six  convolutions, 
situated  in  the  bifurcation  of  the  fissure  of  Sylvius  ;  and  hidden 
under  the  fused  lower  extremity  of  convolutions  which  belong- 
to  the  frontal  and  parietal  lobes. 

The  Convolutions  and  Sulci  of  the  /^r<9;z/rt/Zo<^^  are  usually 
described  as  consisting^  of  two  sets,  those  found  on  the  exter- 
nal surface,  and  those  on  the  inferior  surface,  which  is  fre- 
quently described  as  the  Orbital  Lobe.  The  subdivision  is 
unnecessary,  the  convolutions  being-  continuous  with  one 
another.  In  brains  with  a  small  number  of  convolutions  it  will 
be  seen  that  in  front  of  the  fissure  of  Rolando,  and  running- 
parallel  with  it,  is  a  sulcus  of  the  same  character,  but  of  less 
depth.  This  is  called  the  prccoitral  sulcus.  It  commences 
near  the  bifurcation  of  the  fissure  of  Sylvius  and  passes 
upward  nearly  to  the  g-reat  long-itudinal  fissure.  This  sulcus 
cuts  off  a  convolution  bounded  in  front  by  the  precentral 
sulcus  and  behind  by  the  fissure  of  Rolando,  which  is  known 
as  the  ascending  frontal  convolution.  Two  small  sulci  extend 
forward  from  near  the  precentral  sulcus.  Sometimes  they 
run  into  the  precentral  sulcus  ;  but  as  a  rule  they  do  not. 
These  extend  straight  forward  to  the  anterior  extremity  of 
the  frontal  lobe,  cutting-  off  short  convolutions,  which  are 
known  from  above  downward  -^l^  first,  seco/id,  and  third  fron- 
tal convolutions,  or  occasionally  as  superior  middle,  and 
inferior  frontal  convolutions.  If  these  convolutions  be  traced 
around  to  the  inferior  surface  of  the  frontal  lobe,  it  will  be 
seen  that  here  also  are  three  convolutions,  sometimes  described 
as  they/r67,  second,  and  third  orbital  co}ivolutions,  numbered 


396  DESCRIPTIVE  ANATOMY. 

from  within  outward  and  backward  ;  but  in  reality  the  con- 
tinuation of  the  first,  second,  and  third  frontal  convolutions. 
On  the  orbital  surface,  close  to  the  g-reat  longitudinal  fissure, 
is  a  narrow  but  deep  sulcus,  which  lodg-es  the  olfactory  nerve. 
External  to  this  is  another  sulcus,  less  well-marked,  which  is 
the  external  boundary  of  the  first  orbital  convolution,  the  con- 
tinuation of  the  first  frontal.  The  second  sulcus,  marking  off 
the  second  and  third  orbital  convolutions,  or  middle  and  infe- 
rior frontal  convolutions,  runs  transversely,  and  is  usually 
divided  into  two  or  more  limbs,  so  that  the  second  orbital  con- 
volution lies  in  front  of  the  third. 

The  ascending-  frontal  convolution  begins  below  near  the 
bifurcation  of  the  Sylvian  fissure,  and  is  connected,  around  the 
lower  end  of  the  precentral  sulcus,  with  the  third  frontal  con- 
volution, forming  a  part  of  the  operculum.  Generally,  also, 
it  is  connected,  around  the  lower  end  of  the  fissure  of  Rolando, 
with  the  ascending  parietal  convolution  ;  and  these  two  con- 
volutions are  nearly  always  united  around  the  upper  end  of 
the  Rolandic  fissure. 

The  first,  or  superior,  frontal  convolution  is  limited  above 
by  the  longitudinal  fissure  and  below  by  the  first  frontal  sul- 
cus. It  passes  directly  forward  from  the  precentral  sulcus, 
around  the  upper  end  of  which  it  is  connected  with  the  ascend- 
ing frontal  convolution,  and,  winding  around  the  anterior 
extremity  of  the  frontal  lobe,  becomes  continuous  with  the 
so  called  first  orbital  convolution.  On  its  orbital  surface  this 
convolution  is  marked  by  a  deep  antero-posterior  sulcus — the 
olfactory. 

The  second,  or  middle  frontal  convolution  is  bounded  above 
by  the  first,  and  below  by  the  second  frontal  sulcus.  It  is 
shorter  than  the  preceding  convolution,  with  which  it  fuses 
around  the  end  of  the  first  sulcus.  Passing  around  the  front 
of  the  frontal  lobe,  it  becomes  continuous  with  the  second  orbi- 
tal convolution,  which  occupies  the  antero-external  aspect  of 
the  orbital  surface  of  the  frontal  lobe. 

The  third,  or  inferior,  frontal  convolution  is  cut  off  from 
the  second  by  the  second  frontal  sulcus,  but  fuses,  around  the 


THE  CENTRAL  NERVOUS  SYSTEM.  397 

posterior  extremity  of  that  sulcus,  with  that  convolution.  It 
is  very  short  and  does  not  reach  the  anterior  extremity  of  the 
hemisphere,  but  winds  around  its  outer  aspect  to  become  con- 
tinuous with  the  third  or  posterior  orbital  convolution. 

The  Convolutions  of  the  Pai'ietal  Lobe  are  the  Ascending" 
Parietal,  the  Superior  Parietal,  and  the  Inferior  Parietal. 

The  Ascending-  Parietal  is  cut  off   by  the    intra-parietal 
sulcus. 

This  is  one  of  the  most  variable  sulci  on  the  outer  surface 
of  the  hemisphere.  It  consists  of  three  limbs,  which  may  or 
may  not  be  joined  tog-ether.  Commencing"  above  the  fissure 
of  Sylvius,  it  passes  upward  and  backward  parallel  with  and 
behind  the  fissure  of  Rolando  to  near  the  g-reat  longitudinal 
fissure.  From  a  little  above  its  centre  a  branch  passes  nearly 
directly  backward,  separating"  the  superior  from  the  inferior 
parietal  convolutions.  The  vertical  portion  of  this  sulcus  is 
named  the  Post-central;  the  whole  is  called  the  Intraparietal 
Sulcus.  This  may  consist  of  three  separate  and  distinct  sulci, 
or  any  two  of  these  may  be  united,  and  the  third  one  exist  as 
a  separate  sulcus. 

That  portion  of  the  lobe  which  is  bounded  in  front  b}^  the 
fissure  of  Rolando,  and  behind  by  the  ascending"  portion  of  the 
post-central  sulcus  is  called  the  ascending  parietal  convolution. 
That  portion  between  the  g"reat  long"itudinal  fissure  above,  the 
horizontal  portion  of  the  post-central  sulcus  below,  and  the 
external  portion  of  the  parieto-occipital  fissure  behind,  is  called 
the  superior  parietal  convolution.  That  part  which  lies  be- 
tween the  horizontal  limb  of  the  fissure  of  Sylvius  below,  and 
the  intra-parietal  sulcus  above  and  in  front,  is  called  the  inferior 
parietal  convolutioji.  This  inferior  parietal  convolution  is 
frequently  divided  by  a  small  secondary  sulcus  into  two  por- 
tions, an  anterior  lying"  above  the  fissure  of  Sylvius,  called  the 
supramarginal ,  and  a  posterior,  which  extends  around  the 
horizontal  limb  of  the  fissure  of  Sylvius  and  blends  with  the 
occipital  lobe,  called  the  angular  gyrus,  or  convolution. 

It  will  be  seen  that  the  fissure  of  Rolando  reaches  neither 
the  g-reat  longitudinal  fissure  nor  the  fissure  of  Sylvius,  hence 


398  DESCRIPTIVE  ANATOMY. 

around  the  two  extremities  of  this  fissure  the  ascending  frontal 
and  ascending  parietal  convolutions  communicate  with  one 
another.  At  the  lower  extremity  of  the  fissure  of  Rolando 
the  ascending  frontal  convolution  communicates  with  theascend- 
ing  parietal,  and  also  with  the  third  frontal  convolution.  That 
portion  which  connects  with  the  third  frontal  convolution  lies 
in  the  interval  between  the  two  limbs  of  the  fissure  of  Sylvius, 
and  forms  the  overhanging  portion  of  brain  substance,  the 
Operculum,  which  conceals  the  Island  of  Reil. 

The  Convohitions  of  the  Occipital  Lobe  are  three  in  number, 
superior,  middle,  and  inferior.  These  convolutions  are  separa- 
ted by  tw^o  sulci,  called  the  superior  and  middle  occipital 
sulci. 

These  sulci  are  indistinct  and  poorly  marked,  each  extend- 
ing backward  on  the  occipital  lobe,  the  convolutions  being 
named  from  above  downward.  First,  Second,  and  Third,  or 
Superior,  Middle,  and  Inferior.  The  superior  occipital  con- 
volution is  connected  with  the  parietal  lobe  ;  the  middle  and 
inferior  with  the  temporo-sphenoidal  lobe. 

The  Convolutions  of  the  Temporo-Sphejioidal  Lobe.  This 
lobe  is  divided  by  three  sulci  into  five  convolutions,  though 
two  of  these  convolutions  are  found  on  the  inner  surface  of  the 
hemisphere.  The  two  sulci  found  on  the  outer  surface  are 
the  superior,  or  parallel  sulcus  and  the  middle,  or  second  tem- 
poral, sulcus.  The  superior,  or  parallel,  sulcus  receives  its 
name  from  being  parallel  with  the  fissure  of  Sylvius  ;  the 
second,  or  middle  temporal,  sulcus  is  smaller  and  much  less 
distinctly  marked. 

Ti\lq.  first  temporo-sphenoidal  convolution 'v^  bounded  above 
by  the  horizontal  limb  of  the  fissure  of  Sylvius,  and  below  by 
the  parallel  sulcus.  At  its  posterior  extremity  it  is  continuous 
vs'ith  the  ang'ular  gyrus  of  the  parietal  lobe.  The  second 
teniporo-sphenoidal  convolution  lies  between  the  parallel  sul- 
cus and  the  second  temporal  sulcus,  and  is  continuous  poste- 
riorly with  the  angular  gyrus  of  the  parietal  and  the  second 
occipital  convolution. 

The  third  temporo-sphenoidal,  lying  below^  the  second  tern- 


THE  CENTRAL  NERVOUS  SYSTEM.  399 

poral  sulcus,  is  continuous  posteriorly  with  the  third  occipital 
convolutton. 

The  Island  of  Rcil.  On  reaching;-  the  operculum  a  o-roup 
of  five  or  six  convolutions  (thouo-h  as  few  as  three  have  been 
observed)are  found  lyincr  in  the  interval  between  the  diverg-ing- 
limbs  of  the  fissure  of  Sylvius.  These  convolutions  constitute 
the  island  of  Reil.  The  sulci  are  only  slig-ht  depressions,  and 
the  convolutions  slig-ht  elevations.  They  all  run  in  the  same 
direction,  upward,  backward,  and  inward. 

Sulci  and  Convolutions  on  the  Internal  Face  of  the        ^ 
Hemisphere. 

The  Calloso-mar^inal  Sulcus  commences  near  the  base  of 
the  brain  beneath  the  termination  of  the  corpus  callosum.  It 
runs  at  first  forward,  following-  the  rostrum  of  the  corpus 
callosum,  winds  around  its  jgenu,  thence  backward,  parallel 
with  the  body  of  the  corpus  callosum,  until  it  reaches  the 
posterior  third  of  the  brain,  when  it  abruptly  turns  upward 
and  passes  to  the  g-reat  long-itudinal  fissure. 

The  Parieto-occipital,  the  second  sulcus  found  on  the  inner 
face,  begfins  at  the  splenium  of  the  corpus  callosum,  and  passes 
upward  and  backward  to  terminate  on  the  external  face  of  the 
hemisphere. 

The  Calcarine  Fissure,  or  Sulcus,  is  the  third  of  the  sulci 
found  on  the  inner  face.  It  commences  by  a  forked  extremity 
near  the  end  of  the  occipital  lobe,  and  runs  nearly  directly  for- 
ward, with  a  slight  inclination  downward  ;  and  joins  the 
parieto-occipital  sulcus  at  an  acute  ang-le. 

The  Collateral  Sulcus.  The  fourth  is  a  long-  sulcus  which 
extends  across  the  inner  face  of  the  temporo-sphenoidal  lobe, 
separating-  the  fourth  and  fifth  temporo-sphenoidal  convolu- 
tions.    It  is  called  the  Collateral  Sulcus. 

The  Dentate  Sulcus,  the  last  one,  passes  beneath  the  splen- 
ium of  the  corpus  callosum  to  terminate  near  the  commencement 
of  the  fissure  of  Sylvius. 

Of  these  sulci,  the  calcarine,  the  collateral,  and  the  dentate 
all  make  appearances  in  the  cavities  found  in  the  interior  of  the 
brain.     The  calcarine  sulcus  forms  the  Hippocampus  Minor, 


400  DESCRIPTIVE  ANATOMY. 

or  Calcar  Auis  (L.  A  bird's  spur),  in  the  posterior  horn  of  the 
lateral  ventricle.  The  collateral  sulcus  forms  the  eniinentia 
collateralis  ;  and  the  hippocampal,  or  dentate,  sulcus  forms, 
the  Hippocampus  Major  in  the  descending-  horn  of  the  lateral 
ventricle. 

These  sulci  divide  the  internal  surface  into  a  marginal  con- 
volution, the  g"yrus  fornicatus,  the  quadrate  lobe,  the  cuneate, 
the  uncinate  g-yrus,  and  the  fourth  and  fifth  temporo-sphenoidal 
lobes. 

The  Marg-inal  Convolution  is  the  inner  face  of  the  frontal 
lobe.  It  commences  at  the  anterior  parf orated  space,  follows 
the  winding's  of  the  calloso-marg-inal  sulcus,  then  runs  forward 
beneath  the  rostrum  of  the  corpus  callosum,  winds  upward 
around  the  g^enu,  and  passes  backward  until  the  calloso-mar- 
ginal  sulcus  turns  upward  to  the  g-reat  longitudinal  fissure, 
where  the  convolution  terminates,  and  is  separated  from  the 
parietal  lobe  by  the  end  of  this  sulcus.  It  will  be  seen  that 
this  convolution  corresponds  to  the  inner  face  of  the  first  orbi- 
tal, the  first  frontal,  the  ascending  frontal  and  ascending 
parietal  convolutions. 

The  Gyrus  Fornicatus .  Below  the  marginal  convolution 
and  between  the  calloso-mirginal  sulcus  and  the  corpus  cal- 
losum is  the  Gyrus  Fornicatus ,  or  convolution  of  the  corpus 
callosum.  It  follows  the  same  course  as  the  preceding  sulcus 
until  it  reaches  the  posterior  extremity  of  the  corpus  callosum, 
where  it  blends  with  the  quadrate  lobe,  winding  around  the 
splenium  of  the  corpus  callosum.  Here  it  changes  its  name 
to  become  the  uncinate,  or  hypocampal,  convolution. 

The  .Quadrate  Lobe  is  bounded  in  front  by  the  upturned 
portion  of  the  calloso-marginal  sulcus,  behind  by  the  parieto- 
occipital sulcus.  Above,  it  is  limited  by  the  great  longitudi- 
nal fissure  ;  and  below  it  blends  with  the  gyrus  fornicatus. 
It  is  the  internal  face  of  the  superior  parietal  convolution. 

The  Cuneate  Lobe  (L.  Cuneus,  a  wedge)  is  bounded  in  front 
by  the  parieto-occipital  sulcus,  and  below  by  the  calcarine 
sulcus ;  and  is  the  internal  face  of  the  first  and  second  occipi- 
tal convolutions. 


THE  CENTRAL  NERVOUS  SYSTEM.  401 

The  Hippocanipal,  or  Uiicinate,  Lobe  (L.  Unciiius,  hooked) 
is  a  continuation  downward  and  forward  of  the  gyrus  foruica- 
tus.  It  is  bounded  above  by  the  dentate  fissure,  and  below  by 
the  collateral  fissure.  It  extends  as  far  forward  as  the  com- 
mencement of  the  fissure  of  Sylvius;  and  innerwards  to  the  point 
where  the  g'yrus  fornicatus  commences.  Here  it  turns  back- 
ward upon  itself,  forrainof  the  hook-shaped  appearance  which 
g-ives  the  convolution  its  name.  It  is  the  fifth  temporo-sphe- 
noidal  convolution,  the  fourth  temporo-sphenoidal  lying-  beneath 
the  collateral  sulcus. 

In  addition  to  these  convolutions,  when  the  hemispheres  are 
separated  by  cutting'  throug-h  the  corpus  callosum  we  of  course 
see  the  fibres  composing-  the  corpus  callosum  and  the  inner 
face  of  the  optic  thalamus. 

The  Base  of  the  Brain. 

The  lower  surface,  or  base,  of  the  brain,  is  very  irreg-ular 
in  outline,  because  it  is  fitted  into  the  fossae  of  the  skull. 
A^teriorl^^  on  either  side,  is  seen  the  orbital  face  of  the  frontal 
lobe  which  is  somewhat  triang-ular  with  the  base  backward 
and  apex  forward.  Behind,  and  prolong-ed  downward  to  fit 
in  the  middle  fossa,  is  the  temporo-sphenoidal  lobe,  and,  behind 
this,  the  occipital,  also  triang-ular  with  its  base  forward,  flat- 
tened by  pressure  on  the  tentorium.  The  numerous  appear- 
ances found  on  the  base  of  the  brain  may  be  best  studied  by 
dividing-  them  into  two  sets,  viz:  those  which  occur  in  pairs, 
and  lie  on  either  side  of  the  mid-line;  and  those  which  are 
sing-leand  occupy  the  mid-line. 

Beginning-  on  the  mid-line  in  front  and  passing-  backward, 
we  find  the  following- appearances,  viz  :  The  g-reat  long-itudinal 
fissure,  with  the  rostrum  of  the  corpus  callosum  seen  at  its 
bottom;  the  opticchiasm;  the  pituitary  body,  infundibulum  and 
tuber  cinerium  leading-  the  one  to  the  other;  the  posterior 
perforated  space  ;  the  transverse  fibres  of  the  pons  ;  the  slig-ht 
median  depression  on  the  pons;  the  fissure  between  pons  and 
medulla,  and  the  anterior  median  fissure  of  the  medulla. 

The  appearances  occurring- in  pairs  and  described  on  one  side 
only,  are:  The  orbital  face  of  the  frontal  lobe  with  its  two  sulci 

Des  Anat— 26 


402  DESCRIPTIVE  ANATOMY. 

and  three  convolutions;  the  peduncles  of  the  corpus  callosum; 
the  groove  or  sulcus  for  the  olfactory  nerve  and,  the  olfactory 
bulb,  and  nerve,  with  the  three  roots  of  the  latter;  the  beginninof 
of  the  fissure  of  Sylvius;  the  optic  nerve,  internal  to  the  roots  of 
the  olfactory;  the  anterior  perforated  space  ;  the  optic  tract 
crossing:  the  crus  cerebri,  and,  internal  to  this,  a  corpus  albi- 
ans;  and,  from  this  point  backward,  the  roots  of  the  cranial 
nerves. 

The  long'itudinal  fissure  and  the  corpus  callosum  are  else- 
where described.  The  optic  chiasm  is  formed  by  the  union 
of  the  two  optic  tracts  and  gives  off  the  optic  nerves.  It  will 
be  described  with  these  nerves.  The  pituitary  body,  or  hypo- 
physis cerebri,  is  situated  in  the  sella  Trucica,  bound  down  by 
a  process  of  the  dura  mater.  It  consists  of  two  lobes,  anterior 
and  posterior,  separated  by  a  fibrous  lamina,  the  latter,  during- 
foetal  life,  communicating  with  the  third  ventricle  through 
the  infundibulum.  The  infundibuluin  is  a  small  tube  of  grey 
matter  attached  above  to  the  lamina  cineria  and  below  to  the 
infundibulum.  It  always  communicates  with  the  third  ventri- 
cle. The  laviina  cineria,  or  tuber  cinerium,  is  a  small  mass 
of  g"rey  matter  which  forms  part  of  the  floor  of  the  third 
ventricle.  It  is  connected  with  the  upper  face  of  the  optic 
chiasm  and  extends  back  to  the  carpora  albicantia. 

^yx^s^  posterior  perforated  space  is  in  the  triang-le  formed  by 
the  crura  on  either  side  and  the  pons  behind.  It  is  made  by 
a  number  of  small  vessels  which  here  pass  into  the  optic  tha- 
lami.  The  remaining-  appearances  require  no  further  descrip- 
tion. 

The  olfactory  bulb  (usually  destroyed  in  removing- the  brain) 
is  an  oblong-  rounded  mass  of  grey  matter  which  lies  on  the 
cribriform  plate  of  the  ethmoid  and  gives  off  numerous  fila- 
ments to  the  nose.  This  bulb  contracts  to  become  the  olfactory 
nerve  which  leads  back  to  the  fissure  of  S34vius  and  divides 
into  its  three  roots,  which  are  described  with  the  other 
cranial  nerves. 

The  anterior  perforated  space  lies  in  the  commencement  of 
the  Sylvian  fissure.  Antero-internally  it  is  bounded  by  the  optic 


THE  CENTRAL  NERVOUS  SYSTEM.  403 

nerve;  internally,  by  the  optic  chiasm,  postero-internally,  by 
the  optic  tract.  Externally  are  the  Sylvian  fissure  and  the  outer 
root  of  the  olfactory  nerve,  while  the  middle  root  runs  near 
the  centre  of  the  space.  It  is  crossed  by  the  peduncles  of  the 
corpus  callosum,  is  connected  with  the  lamina  cinerium,  lies 
beneath  the  corpus  striatum,  and  receives  its  name  from  being- 
perforated  by  numerous  small  vessels  which  pass  into  the  latter 
body.  The  optic  tract  will  be  described  with  the  cranial 
nerves.  The  cms  cerabri  is  a  round  cord  which  serves  to 
connect  the  pons  with  the  cerebrum.  It  is  about  three  fourths 
of  an  inch  in  leng-th  and  is  composed  of  two  sets  of  long-itudi- 
nal  white  fibres,  superficial  and  deep  (or  anterior  and  poste- 
rior; and  an  intermediate  bundle  of  gray  matter  called  locus 
)iigcr.  The  superficial  white  fibres  pass  through  the  pons 
from  the  anterior  pillars  of  the  medulla  to  the  internal  capsule. 
They  form  what  is  called  the  crusta.  The  deep  lono-itudinal 
fibres,  or  tegmentum,  pass  from  the  olivar}^  body  and  lateral 
and  posterior  columns  of  the  medulla  through  the  pons  to  the 
optic  thalamus  and  cerebral  cortex. 

Situated  at  the  base  of  the  brain  is  a  six-sided  space  called 
the  inter-peduncular  space.  It  is  bounded  in  front,  on  the 
mid-line,  by  the  optic  chiasm;  behind,  on  the  mid-line,  by  the 
transverse  fibres  of  the  pons;  antero-laterally,  by  the  optic 
tract;  postero-laterally,  by  the  crura  cerebri.  The  corpora 
alljicantia  or  niamilluria  are  a  pair  of  small  rounded  bodies, 
situated  just  behind  the  tuber  cinerium,  formed  by  the  anterior 
pillars  of  the  fornix  which  pass  down  to  the  base  of  the  brain 
and  then  turn  upward  to  reach  the  optic  thalami.  It  is  the 
knuckle  formed  by  reversing  their  course  which  forms  the 
corpora  albicantia.  This  space  contains  the  pituitary  body, 
infundibulum,  lamina,  or  tuber,  cinerium,  corpora  albicantia, 
or  mamillaria,  and  the  posterior  perforated  spot.  It,  and  its 
contents,  form  the  floor  of  the  third  ventricle. 

Structure  of  the  Cerebrum. 

When  a  horizontal  slice,  an  inch  or  so  thick,  is  removed  from 
the  upper  surface  of  one  hemisphere,  the  cut  surface  shows  a 
central,  oval,  white  portion  surrounded,  on  the  exterior,  by  a 


404  DESCRIPTIVE  ANATOMY. 

serrated  grayish  border;  this  is  known  as  the  centrum  ovale 
minus.  When  both  hemispheres  have  been  cut  to  the  same  level, 
and  this  level  corresponds  to  the  depth  of  the  central  portion  of 
the  longitudinal  fissure,  two  centra  ovalia  minora  are  produced, 
connected  in  the  centre  by  transverse  fibres,  forming-  a  connect- 
ing band,  called  the  corpus  callosum;  and  the  whole  appearance, 
formed  by  the  two  centra  ovalia  minora  and  the  corpus  callosum, 
is  called  the  centrum  ovale  majus. 

Corpus  Callosum. 

The  corpus  callosum  consists  almost  entirely  of  transverse 
fibres  passing  from  one  hemisphere  to  the  other.  Upon  its 
upper  surface  there  is  a  shallow  groove,  extending  from  before 
backw^ard  along  the  middle  line,  called  the  raphe;  bordering 
each  side  of  the  raphe  is  a  slight  ridge  produced  by  a  bundle 
of  longitudinal  fibres,  the  two  ridges  being-  called  the  nerves 
of  Lancisi.  E^xternal  to  these  are  seen  a  few  other  longitudi- 
nal fibres,  producing  slight  ridges  which  are  called  the  lateral 
longitudinal  strise.  When  the  corpus  callosum  is  bisected 
longitudinally  it  is  seen  to  be  about  four  inches  long  and  to 
bend  vertically  downw^ard  both  in  front  and  behind.  The 
bent,  rounded,  posterior  extremity  is  called  the  splenium,  or 
pad,  or  bulb,  the  central  portion  the  body,  and  the  anterior 
bent  portion  the  genu,  which  turns  backward  beneath 
the  body  for  a  short  distance  under  the  name  of  the  rostrum. 
The  rostrum  divides  into  two  cords  called  peduncles,  which 
pass  downward  and  backward  to  the  base  of  the  brain  to 
terminate  at  the  anterior  perforated  space.  Contained  in  the 
substance  of  the  brain,  between  its  base  and  the  corpus  callo- 
sum, is  an  irregular  cavity  divided  into  several  parts,  two  of 
which  are  known  as  the  lateral  ventricles,  while  the  space 
is  spoken  of  as  the  general  ventricular  cavity. 

The  General  Ventricular  Cavity. 

The  Ventricular  Cavity  is  a  space  found  in  the  interior  of 
the  brain,  divided  into  two  lateral,  or  first  and  second  ventri- 
cles, and  third  and  fourth  ventricles,  these  cavities  all  com- 
municating  with   one   another    by  means  of  small  foramina. 


THE  CENTRAL  NERVOUS  SYSTEM.  405 

The  g-eneral  ventricular  cavity  exists  between  the  corpus 
callosum  and  velum  interpositum  above,  the  interpeduncular 
space  at  the  base  of  the  cerebrum,  and  the  upper  surface  of  the 
pons  varolii  and  the  medulla  oblong-ata  below.  The  lateral 
ventricles  exist  in  the  two  hemispheres  of  the  cerebrum,  sepa- 
rated from  one  another  on  the  mid-line  by  a  thin  septum. 
The  third  ventricle  lies  below  the  two  lateral  ventricles,  and 
the  fourth  is  below  and  behind  the  lateral  ventricles,  occupy- 
ing- a  position  on  the  medulla  and  the  pons. 

The  Lateral  Ventricles. 

The  rig-ht  is  usually  described  as  the  first,  and  the  left  as 
the  second,  lateral  ventricle.  The  corpus  callosum  forms  a 
part  of  the  roof  of  the  ventricular  cavity  ;  and  upon  its  re- 
moval, the  floor,  formed  of  various  objects,  is  brougfht  into  view. 
Bach  lateral  ventricle  consists  of  a  body,  and  three  extensions, 
called  the  horns  of  the  ventricle,  anterior,  posterior,  and 
middle.  The  entire  cavity  is  roofed  over  in  part  by  the  cor- 
pus callosum,  and  in  part  by  the  frontal,  parietal,  occipital, 
and  tempero-sphenoidal  lobes.  The  inner  zuall  is  formed  in 
part  by  a  portion  of  brain  tissue  called  the  Seftiun  Liicidum 
(L.  Transparent  Septum).  The  outer  zuall  is  the  point  of 
junction  of  the  corpus  callosum  with  the  fibresof  the  cerebrum, 
while  the  floor  is  composed  of  a  larg-e  number  of  objects,  which 
will  be  enumerated  later.  The  body  of  the  ventricle  is  all  of 
that  portion  which  exists  between  the  anterior  horn  and  the 
middle  and  posterior  horns.  Its  upper  boundary  is  the  lower 
surface  of  the  corpus  callosum;  its  inner  boundary  is,  in  front, 
the  septum  lucidum,  and,  behind  that,  the  junction  of  the  fornix 
and  the  corpus  callosum;  its  outer  wall  is  the  junction  of  the 
corpus  callosum  with  the  fibres  of  the  cerebrum.  The  floor 
from  before  backward  is  made  up  of  the  corpus  striatum,  the 
tenia  semicircularis,  or  horny  bind  of  Tarinus,  the  optic 
thalamus,  the  choroid  plexus,  and  the  fornix.  E)ach  of 
these  requires  a  separate  description. 

The  Corpus  Slriatinn{\^.  .S7m///^6-,g-rooved  or  furrowed)  is  an 
oblong-,  or  pear-shaped,  g-ravish  mass,  with  its  larg-e  end  in 
front.      It   is  divided   into  two  portions,   called  the  ititra-  and 


406  DESCRIPTIVE  ANATOMY. 

extra-  ventricular  -portions^  the  former  being-  also  known  as 
the  caudate  nucleus  and  the  latter  as  the  lenticular  nucleus. 
Between  these  two,  on  the  outer  wall  of  the  ventricle,  is  a 
portion  of  white  matter,  called  the  inte7-nal  capsule.  External 
to  this  comes  the  extra- ventricular  portion,  the  nucleus  lenticu- 
laris  (Iv.  lense-shaped) ;  and  on  the  outer  face  of  this  ag-ain  is  a 
mass  of  white  matter,  called  iho,  etxer7ial  capsule.  The  white 
matter  which  descends  between  the  two  portions  of  the  corpus 
striatum,  and  on  the  outer  side  of  the  nucleus  lenticularis, 
transmits  impulses  from  the  surface  of  the  hemisphere  to  the 
medulla  oblong-ata,  and  throug-h  that  to  the  spinal  cord. 

The  Tenia  Semicircularis  is  a  rounded  cord,  which  lies  in 
the  groove  between  the  corpus  striatum  and  the  optic  thalamus  • 
It  may  be  traced  into  the  descending-  horn  of  the  lateral  ventri- 
cle, where  it  joins  with  the  anterior  pillar  of  the  fornix  ;  and 
thence  backward  into  the  roof  of  the  descending*  horn,  where 
it  terminates  in  a  projection  of  gray  matter,  the  Corpus 
Amyg-dalce. 

The  Optic  Thalamus  \%  amass  of  gray  matter  which  projects 
into  the  floor  of  the  body  of  the  lateral  ventricle,  and  forms  the 
lateral  walls  of  the  third  ventricle.  It  will  be  described  in 
connection  with  that  ventricle. 

The  Fornix  (L.  Fornix,  an  arch,  or  vault)  is  a  long"itudinal 
band  of  white  matter  lying-  beneath  the  corpus  callosum;  and 
blended  with  its  fellow  of  the  opposite  side  behind,  but  separate 
in  front.  Behind  it  thins  out  into  a  broad,  flattened  band,  the 
outer  edg-e  of  which  is  called  the  corpus  fimbriatum  (L.  Fim- 
bria., an  edg-e,  or  border).  It  descends  into  the  floor  of  the 
descending-  horn,  covering-  the  projection  in  that  space  known 
as  the  hippocampus  major.  Between  the  two  posterior  pillars 
of  the  fornix  transverse  fibres  are  stretched,  which  from  their 
supposed  resemblance  to  a  harp  have  g-iven  the  name  of  lyra  to 
this  portion  of  the  fornix.  These  posterior  fibres  blend  with 
the  white  matter  forming- the  hippocampus  major.  Anteriorly 
the  two  pillars  descend  to  the  base  of  the  brain,  not  connected 
by  transverse  fibres,  and  pass  downward  to  the  corpora 
mamillaria,  where  they  reverse  their  course  and  turn  upward, 


THE  CENTRAL  NERVOUS  SYSTEM.  407 

to  be  lost  in  the  optic  thalamus  of  the  corresponding"  side. 
The  anterior  pillars  of  the  fornix  are  connected  with  the  pe- 
duncles of  the  pineal  g-latid,  and  receive  fibres  from  the  septum 
lucidum. 

The  Choroid  Plexus  passes  along-  the  edg"e  of  the  most  in- 
ternal object  in  the  ventricle,  the  fornix.  It  is  a  mass  of  blood 
vessels  arrang-ed  in  the  folds  of  the  pia  mater,  which  here 
projects  into  the  interior  of  the  brain.  These  vessels  enter  the 
descending-  horn  of  the  lateral  ventricle,  pass  upward  through 
it,  pass  throug-h  the  body  of  the  ventricle,  and  continue  their 
course  into  the  descending  horn,  at  the  bottom  of  which  other 
small  vessels  unite  with  them.  The  choroid  plexus  of  each 
side  passes  beneath  the  bod}-  of  the  fornix,  unites  with  the 
choroid  plexus  of  the  opposite  side,  and  forms  the  true  roof  of 
the  third  ventricle.  Prom  the  under  surface  of  the  fornix  it 
passes  backward  through  the  transverse  fissure  of  Bichat> 
joins  with  the  velum  interpositum,  forming  there  a  portion  of 
the  roof  of  the  fourth  ventricle  ;  and  becomes  continuous  with 
the  general  pia  matral  covering  of  the  brain. 

Of  the  three  horns  of  the  lateral  ventricle  the  descending  is 
the  largest,  the  anterior  intermediate  in  size,  and  the  posterior 
the  smallest. 

The  Anterior  Horn  passes  downward,  forward,  and  outward, 
curving  around  the  anterior  extremity  of  the  corpus  striatum; 
and  being  entirely  contained  in  the  frontal  lobe  of  the  brain. 

The  Posterior  Horn  is  curved  like  a  half-bent  finger,  or 
cockspur,  extends  backward  into  the  occipital  lobe  ;  and  pre- 
sents on  its  floor  a  slight  projection,  the  hippocampus  minor, 
or  calcar  avis,  which  is  formed  by  the  calcarine  sulcus  already 
described,  on  the  inner  face  of  the  hemisphere. 

The  Descendin<r  Horn  pursues  a  tortuous  course.  It  winds 
around  the  optic  thalamus,  passing  first  outward  and  back- 
ward, then  downward  and  forward;  and  then,  again  changing 
its  direction,  it  passes  downward  forward  and  inward,  to  ter- 
minate near  the  extremity  of  the  temporo-sphenoidal  lobe. 
This  horn  of  the  ventricle  is  found  first  in  the  parietal  lobe; 
l)ut  the  major  portion  of  it  is  in  the  temporo-sphenoidal  lobe. 


408  DESCRIPTIVE  ANATOMY. 

At  the  junction  of  the  descending-  and  posterior  horns  is  a 
slight  eminence,  frequently  absent,  called  the  eminentia  col- 
lateralis  or  -pes  accessorius.  Starting  from  this  is  a  prominent 
projection,  which  follows  the  curvature  of  the  horn  itself,  is 
formed  by  the  dentate,  or  hippocampal,  sulcus,  and  is  called 
the  cor7iu  ammonis ,  (L.  a  ram's  horn),  or  hip-pocam-pus  major, 
and  terminates  in  the  irregular  projections,  marked  by  inter- 
vening elevations  and  depressions,  called  the  -pes  hippocampi. 
Lying  upon  the  hippocampus  major,  and  blended  with  it,  is 
the  thin  lateral  edge  of  the  fornix,  called  the  corpus  fimbriatum, 
while  rising  behind  this  is  that  portion  of  the  choroid  plexus 
which  passes  into  the  descending  horn.  The  gray  matter  in 
the  descending  horn  covering  the  edge  of  the  hippocampus 
major  is  the  investing  gray  matter  from  the  dentate  sulcus, 
and  is  known  as  the  fascia  dentata. 

At  the  junction  of  the  anterior  horn  with  the  body  of  the 
lateral  ventricle  an  opening  is  observed  upon  either  side,  which 
communicates  with  the  third  ventricle,  and  through  which  the 
choroid  plexus  of  the  lateral  unites  with  the  choroid  plexus  of 
the  third  ventricle.  This  opening  is  known  as  the  foramen  of 
Munro. 

It  will  be  noticed  that  the  descending  horn  of  the  lateral 
ventricle  follows  the  course  of  the  optic  thalamus,  and  hence 
that  that  body  forms  the  roof  of  the  descending  horn  through- 
out its  extent. 

The  Third  Ventricle. 

The  Third  Ventricle  of  the  Brain  is  bounded  above  by  the 
choroid  plexus,  above  which  is  found  the  under  surface  of  the 
body  of  the  fornix.  Below  its  /?oor  slopes  from  behind  down- 
ward and  forward  ;  and  is  made  up  of  the  structures  which  are 
included  in  the  interpeduncular  space.  The  lateral  zvalls  are 
formed  by  the  optic  thalami.  Instead  of  a  posterior  wall  there 
is  an  openeng,  the  acqueduct  of  Sylvius,  or  the  iter  a  tertio  ad 
qiiartum  ventriculnm.  The  anterior  voall  is  formed  by  a 
small  bundle  of  gray  matter,  which  is  ciUed  the  anterior  com- 
missure of  the  brain  (L.  committere,  to  join).  This  anterior 
commissure  is  found  at  the  point  where  the  two  frontal  lobes  are 


THE  CENTRAL  XERVO'US  SYSTEM.  409 

nearly  in  contact,  and  consists  of  an  interchange  of  fibres  be- 
tween the  frontal  lobes.  It  lies  just  in  front  of  the  anterior 
pillars  of  the  fornix.  Stretching-  across  from  the  optic  thala- 
mus of  one  side  to  the  same  body  of  the  opposite  side  is  a  second 
commissure,  which  is  called  the  middle,  or  soft,  commissure 
of  tho.  brain.  This  consists  of  the  interchangfe  of  fibres  be- 
tween the  optic  thalami,  and  is  gfenerally  broken  in  the  removal 
of  the  brain.  The  posterior  commissure,  or  third  set  of 
communicating"  fibres  found  in  the  third  ventricle,  extends  be- 
tween the  posterior  extremities  of  the  two  optic  thalami,  and 
consists  of  white  fibres,  the  central  one  bsing-  g"ray,  these 
fibres  forming-  one  of  the  boundaries  of  the  acqueduct  of 
Sylvius.  Above  the  acqueduct  of  Sylvius  is  a  small  reddish- 
gray  body,  the  Pineal  Gland  (L.  Pinea,  a  pine  cone),  from 
which  proceed  two  processes  of  g-ray  matter,  called  the  pedun- 
cles of  the  pineal  g-land.  These  peduncles  pass  forward  on 
the  upper  inner  face  of  each  optic  thalamus  to  terminate  by 
blending-  with  these  bodies.  The  two  unite  behind  in  the  com- 
missure of  the  peduncles  of  the  pineal  g-land. 

An  examination  of  the  third  ventricle  will  show  that  there 
cirQ  four  openings  communicating-  with  other  cavities  of  the 
brain.  Two  are  found  upon  its  antero-lateral  wall,  the  fora- 
mina of  Munro ;  one  in  its  posterior  wall,  the  acqueduct  of 
Sylvius  ;  and  the  fourth  in  the  floor,  the  Infundibulum.  It 
will  be  remembered  that  at  the  base  of  the  brain,  occupying- 
the  anterior  portion  of  the  interpeduncular  space  was  seen  the 
pituitary  body,  the  infundibulum,  the  tuber  cinereum,  and  the 
lamina  cineria.  Throug-h  the  last  three  pass  the  small  open- 
ing- which  leads  from  the  floor  of  the  third  ventricle  down- 
ward to  the  pituitary  body. 

'Y\\^  foramina  of  Munro  are  bounded  above  and  behind  by 
the  anterior  pillars  of  the  fornix,  in  front  by  the  anterior  com- 
missure. Throug-h  these  two  opening-s  the  choroid  plexus  of 
the  lateral  ventricles  descends  into  the  third.  They  present  a 
somewhat  Y-shax)ed  appearance,  the  tail  of  the  Y  being-  repre- 
sented by  the  union  of  the  choroid  plexuses,  while  the  two  arms 
are  represented  by  the  foramina  of  Munro.  Thus  while  the 
two  lateral    ventricles    communicate    with   one    another,    the 


410  DESCRIPTIVE  ANATOMY. 

communication  is  indirect.  In  order  that  fluid  may  pass  from 
one  lateral  ventricle  to  the  other  it  is  necessary  to  pass  from  the 
right  lateral  ventricle  into  the  third  ventricle,  down  to  the 
tail  of  the  Y;  then  to  ascend  through  the  left  .foramen  of  Munro 
along-  the  second  arm  of  the  Y  into  the  left  lateral  ventricle. 
The  Acqiieduct  of  Sylvius,  the  opening-  in  the  posterior 
wall,  passes  downward  and  backward,  running-  beneath  the 
four  projections  of  brain  substance,  called  the  corpora  quad- 
rigeniina  i^.  fourfold  bodies),  and  pisses  into  the  superior 
angle  of  the  fourth  ventricle.  The  communication  thus 
established  shows  the  general  ventricular  cavity  to  be  continu- 
ous, the  right  and  left  lateral  communicating  through  the 
intervention  of  the  third  and  the  foramina  of  Munro,  the  third 
in  its  turn  communicating  through  the  acqueduct  of  Sylvius 
with  the  fourth,  and  the  fourth  again  by  the  foramen  of 
Arantius  communicating  w^ith  the  ventricular  cavity  found  in 
the  spinal  cord. 

The  Fifth  Ventricle. 

The  Fifth  Ventricle  is  described  in  the  brain  as  consist- 
ing of  the  minute  space  between  the  two  layers  of  the  septum 
lucidum.  It  should  be  borne  in  mind,  however,  that  the  fifth 
ventricle  has  no  connection  with  the  general  ventricular  cavity  ; 
but  that  the  brain  being  developed  from  two  separate  centres, 
one  on  either  side  of  the  body,  unites  in  the  septum  lucidum 
to  form  the  division  between  the  two  lateral  ventricles.  The 
space  between  the  two  layers  of  which  this  septum  is  com- 
posed is  spoken  of  as  the  fifth  ventricle  ;  and  it  therefore  bears 
no  resemblance  to  the  general  ventricular  cavity. 

'^\\Q  fourth  ventricle,  rising  behind  the  pons  and  the  medulla 
will  be  described  in  connection  with  these  portions  of  the  brain. 

The  Medulla  Oblongata. 

Extending  from  the  foramen  magnum,  or  upper  border  of  the 
atlas  to  the  posterior  border  of  the  pons  Varolii,  is  found  the 
medulla  oblongata,  thus  establishing  connection  between  the 
spinal  marrow  and  the  brain.  It  is  conical  in  shape,  with  the 
larger  end  above  and  forw^ard,  and  is  about  one  and  one-fourth 
inches  in  length.     Passing  down  its  centre  in  front  is  the  ante- 


THE  CENTRAL  NERVOUS  SYSTEM.  411 

rior  median  fissure,  and  similarly  marking*  it  behind  is  the 
posterior  median  fissure  ;  these  thoug-h  not  entirely  bisecting- 
it,  serve  to  indicate  its  division  into  lateral  symmetrical  halves. 
Kach  half  is  subdivided  into  four  portions  by  three  long-itudi- 
nal  g-rooves.  Lying-  beside  the  anterior  median  fissure,  and 
separated  by  it  from  its  fellow,  is  the  portion  called  the  corpus 
pyramidale  ;  just  behind  this,  slig^htly  more  bulg-ing-  and  sepa- 
rated from  it  by  a  fissure,  is  a  second  portion  called  the  corpus 
olivare,  being-  visible  for  about  half  an  inch  only.  Behind 
this  a  third  portion  called  the  corpus  restiforme,  separated  by 
a  g-roove  from  the  corpus  olivare  in  front  and  by  another 
slig-ht  g-roove  from  the  fourth  portion,  the  posterior  pyramid, 
wihch  lies  behind  the  corpus  restiforme,  beside  the  posterior 
median  fissure  by  which  it  is  separated  from  its  fellow.  The 
two  posterior  pyramids  are  small  below,  but  as  they  are  fol- 
lowed up  they  suddenly  dilate  into  a  bulbous  enlarg-ement, 
and  ag-ain  as  suddenly  decreasing-,  separate  as  they  ascend  and 
leave  between  them  an  ang-ular  interval  called  the  calamus 
scriptorius — writer's  pen.  When  the  medulla  oblong-ata 
reaches  the  pons  Varolii  it  seems,  on  superficial  veiw,  to  stop 
short,  but  if  the  surface  fibres  of  the  pons,  which  are  trans- 
verse in  direction,  are  peeled  off,  it  is  seen  that  the  pons,  in 
its  centre,  consists  of  vertical,  or  long-itudinal  fibres,  which 
are  continuous  with  the  fibres  of  the  medulla  oblong-ata  below, 
and,  being-  g-athered  into  two  bands,  emerge  from  its  anterior 
border  as  the  two  crura  cerebri. 

The  Fourth  Ventricle. 

The  Fourth  Ventricle  is  diamond-shaped,  having- a  superior 
and  an  inferior  ang-le  and  two  lateral  angles.  The  inferior 
angle  is  formed  by  the  diverging  posterior  pillars  and  the 
restiform  bodies  of  the  medulla;  the  superior  angle  being 
formed  by  the  peduncles  of  the  cerebellum,  The  two  lateral 
angles  are  formed  by  the  junction  of  the  superior  cerebellar 
peduncles  with  the  inferior.  The  superior  angle  is  formed  by 
the  divergence  of  the  superior  peduncles;  and  the  inferior 
angle  by  the  divergence  of  the  inferior  peduncles. 

At  the  superior  angle   is    seen   the  lower   opening  of   the 


412  DESCRIPTIVE  ANATOMY. 

acqueduct  of  Sylvius;  at  the  inferior  angle  is  seen  the 
opening"  of  the  ventricle  of  Arantius. 

The  roof  of  the  fourth  ventricle  is  formed  above  by  that 
small  portion  of  gray  matter  which  stretches  across  from  the 
peduncle  of  one  side  to  the  peduncle  of  the  opposite  side,  and 
v^hich  is  called  the  superior  medullary  velum,  or  more  fre- 
quently, the  Valve  of  Vieusscns.  The  lower  portion  of  the 
roof  is  formed  by  the  velum  interpositum,  above  which  is 
found  the  lower  surface  of  the  cerebellum. 

The  upper  one-half  of  the  /foor  is  formed  by  the  posterior 
surface  of  the  poas,  and  the  lower  one-half  by  the  posterior 
surface  of  the  medulla  oblongata.  Along  the  mid-line  is  seen 
a  fissure,  the  continuation  of  the  posterior  median  fissure  of 
the  spinal  cord.  Opposite  each  of  the  lateral  angles  is  found 
a  depression,  called  th^ fovea  anterior;  and  parallel  with  the 
median  fissure  are  two  rounded  lobes  of  gray  matter,  called 
the  fasciculi  teretes.  Near  the  central  portion  of  the  ventricle 
is  sometimes  seen  a  violet-colored  streak,  consisting  of  gray 
matter,  lying  just  bsneath  a  thin  covering  of  white  (which 
gives  the  singular  CDlor);  and  called  the  Toenia  Violacea  (L. 
Violet-colored  band)..  On  the  floor  of  this  ventricle  may  be 
seen  the  origin  of  several  of  the  cranial  nerves.  A  few  trans- 
verse fibres  are  seen  extending  across  the  ventricle,  those 
above  the  origin  of  the  eighth  nerve  called  the  Auditory  Striai, 
and  those  below  the  Ivineae  Transversae. 

Corpora  Q,uadrigeniina. 

The  Corpora  ^uadrigeiiiina  are  situated  above  the  acqueduct 
of  Sylvius,  and,  as  their  name  implies,  are  divided  into  four 
bodies,  two  on  either  side  of  the  mid-line.  The  anterior  pair 
are  called  the  nates,  the  posterior  the  testes.  On  the  posterior 
extremity,  or  pulvinar,  of  the  optic  thalamus  are  found  two 
minute  projections,  called  the  corpora  geniculata,  internal  and 
external.  From  the  nates  there  proceed  two  small  white  bands, 
which  pass  forward  to  join  the  internal  geniculate  body  of 
either  side ,  while  from  the  testes  two  more  prominent  bands 
pass  between  the  internal  and  external  geniculate  bodies. 
These  rounded  cords  are  known  as  the  anterior  and  -posterior 


THE  CENTRAL  NERVOUS  SYSTEM.  413 

brachia.  From  the  testes  two  bundles  of  fibres  proceed  down 
ward,  outward,  and  backward  to  join  the  cerebellum.  These 
are  the  siipeyior  -peduncles  of  the  cerebellum^  or  upper  lateral 
boundaries  of  the  fourth  ventricle — processus  e  cerebello  ad 
testes.  It  is  between  these  two  that  the  superior  medullary 
velum,  or  valve  of  Vieussens,  extends. 

The  Pineal  Gland,  a  small  reddish  projection,  lies  between 
the  two  nates.  It  consists  of  two  lobes;  and  in  its  interior  is 
a  minute  cavity,  which  contains  a  small  amount  of  viscid  fluid. 
It  is  held  in  place  by  four  peduncles,  or  cords,  two  of  which 
pass  downward  from  the  base  of  the  g-land  to  the  optic  thalami, 
while  the  other  two  have  been  noticed  in  the  third  ventricle  as 
passing-  forward  alongf  the  upper  lateral  aspect  of  the  optic 
thalami  to  reach  the  anterior  crura  of  the  fornix. 

The  Pons  Varolii. 

The  Pons  Varolii  consists  of  superficial  transverse  fibres  ; 
which,  passing-  across  the  mid-line,  enter  the  lobes  of  the  cere- 
bellum, forming  the  middle  peduncles  of  that  portion  of  the 
encephalon,  and  acting  as  commissural  fibres.  Beneath  this 
layer  of  fibres  are  two  rounded  bundles  of  longitudinal  fibres, 
which  pass  forward  from  the  medulla  to  the  cerebrum  ;  and 
emerging  from  the  anterior  border  of  the  pons,  form  the 
crura  of  the  cerebrum,  the  postero-lateral  boundaries  of  the 
interpeduncular  space.  These  crura  are  found  to  expand  on 
entering  the  corresponding  hemispheres  of  the  cerebrum,  and 
to  assume  a  fan-shaped  appearance,  the  corona  radiata,  or 
bands  of  white  fibres  which  transmit  impulses  from  the  cortex 
of  the  cerebrum  to  the  spinal  cord.  They  are  separated  into 
two  bundles   by  the    thin    layer  of  gray  matter,    called    the 

locus  niger. 

The  Medulla  Oblongata. 

Immediately  below  the  pons  is  seen  the  medulla  oblonf>-ala, 
which  effects  the  junction  between  the  various  portions  of  the 
brain  and  the  spinal  cord.  It  is  about  an  inch  and  one-half  in 
length  and  three  quarters  of  an  inch  wide  at  the  widest  por- 
tion of  it ;  and  presents  for  examination  anterior  and  posterior 
surfaces,   superior   and    inferior   extremities.      Many  writers 


414  DESCRIPTIVE  AXATOMY. 

describe  it  as  having-  lateral  surfaces  in  addition  to  the 
anterior  and  posterior  ;  but  as  the  lower  portion  of  the  med- 
ulla is  almost  completely  circular,  it  is  unnecessary  to  g-ive 
it  more  than  two  surfaces. 

The  anterior  surface,  which  looks  downward  as  well  as 
forward,  rests  upon  the  basilar  process  of  the  occipital  bone  ; 
while  the  posterior  surface,  a  part  of  which  is  flattened  and 
looks  upward  as  well  as  backward,  lies  beneath  the  cerebellum. 

Just  where  the  medulla  joins  the  pons  there  is  a  deep  con- 
striction, or  g-roove,  which  extends  completely  around  the 
medulla  :  but  is  deeper  on  the  anterior  than  on  the  posterior 
face. 

As  the  medulla  transmits  the  fibres  to  and  from  the  spinal 
cord,  it  must  correspond  nearU'  to  the  arrangement  of  the 
cord  itself,  consequently  we  find  pillars  in  the  medulla  corre- 
sponding- in  a  g-reat  measure  to  the  same  pillars  found  in  the 
cord.  They  are  however,  not  so  numerous,  nor  are  they 
arranged  in  preciseU^  the  same  w^ay.  The  medulla,  like  the 
cord,  is  divided  along  its  anterior  and  its  posterior  face  by  two 
vertical  fissures,  which  are  continuous  with  the  anterior  and 
posterior  median  fissures  of  the  cord.  Lying  by  the  side  of 
the  anterior  median  fissure,  and  separated  by  that  fissure  from 
its  fellow,  is  a  small  portion  of  the  medulla,  called  the  anterior 
pyramid.  It  is  the  direct  continuation  upw^ard  of  the  anterior 
pyramid  of  the  cord,  but  also  receives  fibres  belonging  to  the 
crossed  pyramidal  tract  of  the  cord,  so  that  the  decussation 
of  these  fibres  takes  place  before  the  cord  terminates  in  the 
medulla.  Behind  this  anterior  pyramid,  near  the  upper  ex- 
tremity of  the  medulla,  is  an  oblong  projection,  called  the 
olivary  body.  This  olivary  body  is  concealed  in  the  lower 
portion  of  the  cord,  where  the  fibres  are  deepl}^  seated  and 
are  covered  b}"  other  portions  of  the  medulla,  and  above  it  is 
made  prominent  h^  the  divergence  of  the  anterior  pyramid  and 
the  fibres  forming  the  restiform  bod3^  Behind  the  olivary 
body  is  a  large  and  prominent  body,  the  restiform  (Iv.  Restis, 
a  rope  ;  forma,  shape)  -which  carries  the  direct  cerebellar  tract 
of  the  cord,  and  terminates  by  forming  the  inferior  peduncles 
of  the  cerebellum. 


THE  CENTRAL  NERVOUS  SYSTEM.  415 

Next  to  the  rest'form  body  is  the  fourth  and  last  portion  of 
the  medulla,  \h.^  posterior  pyramid,  this  portion  of  the  medulla 
carrying-  the  fibres  which  in  the  cord  are  known  as  the  columns 
of  Goll  and  Burdach.  The  posterior  pyramid,  as  it  passes 
upward,  blends  with  the  restiform  body;  and  the  two  pass  to- 
ofether  into  the  cerebellum  to  form  its  inferior  peduncles.  The 
anterior  pyramids  passing-  throug-h  the  pons  Varolii,  enter  into 
the  formation  of  the  crura  cerebri.  The  olivar}-  fibres  disap- 
pear at  the  upper  extremity-  of  the  medulla,  sinking-  deeply  into 
the  pons,  and  probably  aid  in  forming-  the  commissural  fibres 
which  exist  betw^een  the  two  lobes  of  the  cerebellum  as  the 
superficial  fibres  of  the  pons. 

The  appearances  on  the  posterior  face  of  the  medulla  have 
already  been  described  in  connection  with  the  fourth  ventricle 
of  the  brain. 

The  Cerebellum. 

The  Cerebellum,  or  Little  Brai)i,  is  divided  into  two  hemi- 
spheres by  a  deep  fissure  found  on  its  inferior  aspect  and  a 
projection  found  on  the  superior  face.  In  the  adult  its  relation 
in  weig-ht  to  the  cerebrum  is  variously  stated  as  one  to  thirteen 
and  one  to  twenty,  Cruveilhier  g-iving-  the  latter  proportion. 
It  is  usually  described  as  being-  divided  into  three  lobes,  a 
middle  and  two  lateral,  the  middle  being-  generally  called  the 
"worm",  and  the  two  lateral  the  "hemispheres".  The  hemi- 
spheres and  the  worm  present  a  superior  and  an  inferior 
surface. 

When  viewed  from  above,  the  entire  cerebellum  seems 
undivided,  the  hemispheres  being-  directly  continuous  throug-h 
the  middle  of  the  worm.  They  slope  from  before  downward, 
backward  and  outward. 

On  the  inferior  surface  the  appearance  is  entirely  different. 
Here  a  deep  groove  separates  the  two  hemispheres;  but  the 
g-roove  itself  is  partially  filled  by  the  lower  aspect  of  the  worm, 
which  in  its  turn  is  subdivided  by  fissures  into  three  portions. 
The  g-rfjove  in  which  the  worm  lies  terminates  anteriorly  and 
posteriorly  in  notches,  the  incisura  cercbelli,  a)ilcrior  and 
posterior.     The  anterior  is  the  wider,  and  is  not  so  deep  as  the 


416  DESCRIPTIVE  ANATOMY. 

posterior.  The  worm  extends  into  these  notches,  but  does  not 
completely  fill  them.  The  upper  aspect  of  the  worm  is 
g-enerally  called  the  superior  vermiform  process,  and  the 
lower  the  inferior  vermiform  process.  Its  sides  are  attached 
directly  to  the  hemispheres  of  the  cerebellum;  and  probably 
act  as  commissural  fibres.  On  the  upper  face  the  worm  has 
no  subdivisions;  but  when  viewed  from  below  it  is  seen  to  be 
divided  into  a  flattened  mass  of  gray  matter,  the  Posterior 
Medullary  Velum,  behind  that  a  projection  called  the  Uvula 
(L.  Diminutive  of  Uva,  a  gfrape),  and  behind  that  the  Pyramid. 

Each  hemisphere  of  the  cerebellum  is  divided  into  lobes; 
but  we  do  not  find  in  the  cerebellum  the  convolutions  which 
appear  in  the  cerebrum.  The  cerebellum  presents  a  laminated 
appearance,  the  fissures,  or  sulci,  beino-  deep  and  narrow, 
while  the  laminae  overlap  one  another  throug-hout  the  entire 
area  of  each  hemisphere.  Certain  of  these  sulci,  however,  are 
deeper  and  more  distinctly  marked  than  others,  so  that  it 
becomes  possible  to  divide  the  cerebellum  into  lobes  which  are 
less  distinctly  bounded  than  "the  lobes  of  the  cerebrum. 
There  names  are  fanciful;  and  derived  in  the  main  from  a  sup- 
posed resemblance  to  other  portions  of  the  body. 

On  the  lozoer  surface  of  each  hemisphere,  close  to  the 
median  fissure,  is  a  small  projection  of  the  cerebellum  cut 
off  by  a  deep  fissure,  called  the  Tonsils  from  their  supposed 
resemblance  to  a  gland  in  the  throat.  Beyond  the  tonsils, 
and  cut  off  by  the  second  inferior  cerebellar  fissure,  is  a 
curved  lobe,  which  is  called  the  Digastic.  Next  to  this,  and 
between  the  second  and  third  cerebellar  sulci,  is  a  long  narrow, 
curved  lobe,  which  extends  from  the  median  fissure  behind 
the  pyramid  around  to  the  front  of  the  cerebellum  nearly  as 
far  as  the  anterior  median  fissure.  This  lobe  is  very  narrow, 
and  is  called  the  Slender  Lobe.  Behind  the  slendar  lobe,  and 
occupying-the  posterior  extremity  of  the  cerebellum,  is  another 
long  and  slender  lobe,  which  borders  the  slender  lobe,  extendinof 
from  the  posterior  extremity  of  the  median  fissure  around  to 
the  front  of  the  flocculus.  This  is  known  as  the  -postero- 
infer'ior  Lobe. 


THE  CENTRAL  NERVOUS  SYSTEM.  417 

On  the  upper  surface  the  lobes  are  very  indistinct,  and  can 
scarcely  be  described  as  separate  lobes.  There  are  really  but 
two  lobes  on  the  superior  surface,  the  f>ostero- superior  and 
the  anterior,  or  square,  lobe.  It  will  be  noticed  that  the  infe- 
rior vermiform  process  is  that  portion  of  the  cerebellum  which 
overhangs  the  fourth  ventricle,  and  is  its  indirect  roof,  the 
pia  mater  intervening-  between  the  ventricle  and  the  inferior 
vermiform  process. 

The  Spinal  Cord. 

The  Sphial  Cord  is  the  great  connecting  link  between  the 
brain  and  the  various  members  of  the  body.  It  seems  to 
correspond  partially  to  a  mass  of  insulated  wires,  a  large  por- 
tion of  its  work  being  the  transmission  of  impulses  to  and 
from  the  brain  ;  but  it  contains  nerve  centres  which  in  them- 
selves originate  impulses,  hence  it  is  not  merely  a  bundle  of 
transmitting  fibres.  It  is  markedly  similar  to  the  brain  in 
the  arrangement  of  its  membranes,  and  to  some  extent  in  its 
functions  ;  but  is  dissimilar  in  the  arrangement  of  the  mass  of 
gray  and  white  matter. 

The  Membranes  of  the  spinal  cord,  like  those  of  the  brain, 
are  three  in  number,  and  bear  the  same  names  as  those  of  the 
brain,  the  Dura  Mater,  the  Pia  Mater,  and  the  Arachnoid. 

The  Dura  Mater  of  the  spinal  cord  is,  hov^^ever,  unlike  that 
of  the  brain,  much  too  large  for  the  cord  which  it  envelopes. 
It  lines  the  interior  of  the  spinal  canal,  is  firmly  attached 
to  the  bodies  of  the  vertebrae,  and  sends  off  prolongations  for 
each  of  the  thirty-one  pairs  of  spinal  nerves,  which  accompany 
these  nerves  until  they  leave  the  spinal  column.  The  inner 
face  of  the  dura  mater  is  lined  by  the  arachnoid,  as  is  the  case 
in  the  brain  ;  and  it  should  be  borne  in  mind  that  the 
membranes  of  the  spinal  cord  are  all  directly  continuous  with 
those  of  the  brain. 

The  Arachnoid,  forms  here,  as  in  the  brain,  a  serous  mem- 
brane, covers  the  entire  surface  of  the  cord,  and  lines  the  inner 
face  of  the  dura.  It  does  not  closely  hug  the  cord ;  but  between 
it  and  the  cord  is  found  a  continuation  of  the  mis-named  sub- 
arachnoidean  space.     Between  the  visceral  layer  covering  the 

Des  Anat— 27 


418  DESCRIPTIVE  ANATOMY. 

cord  and  the  parietal  layer  covering-  the  dura  is  a  second  space 
which  is  known  as  the  sub-dural,  and  it  really  lies  between 
the  folds  of  the  arachnoid  itself. 

The  Pia  Mater  covers  the  cord  nearly  as  it  does  the  brain, 
but  with  some  slig-ht  differences.  It  sends  prolong-atious  to 
accompany  the  nerves  which  leave  the  spinal  cord,  it  conveys 
the  blood-vessels  as  in  the  brain;  but  it  also  gives  lig-amentous 
fibres,  which  are  not  found  in  the  cranium.  Between  each 
pair  of  spinal  nerves  will  be  found  a  wedge-shaped  portion 
of  fibrous  tissue,  which  is  derived  from  the  pia,  and  which, 
passing-  to  the  lateral  aspect  of  the  cord,  becomes  attached  to 
it,  while  the  point  of  the  wedg-e  extends  outward  to  blend 
with  the  dura.  These  prolong-ations  form  the  Ligamentum 
Denticulatum,  and  serve  the  purpose  of  retaining-  the  cord 
steadily  in  position,  and  of  preventing  its  movement  in  the 
large  chamber  furnished  for  it  by  the  dura. 

The  Cor^  itself  is  nearly,  though  not  quite,  cylindrical,  be- 
ing slightly  flattened  in  the  antero-posterior  direction.  It  is 
seventeen  or  eighteen  inches  in  length,  and  varies  in  weight, 
as  does  the  brain,  with  the  period  of  life,  cause  of  death,  and 
even  with  the  period  after  death  when  the  cord  is  removed. 
It  corresponds  in  length  to  the  upper  tw^o-thirds  of  the  spinal 
canal  in  the  adult,  though  it  is  longer  comparatively  in  the 
foetus,  extending  here  to  the  bottom  of  the  sacral  canal  ;  but 
apparently  the  vertetwae  grow  more  rapidly  than  the  cord  and 
hence  the  cord  is  carried  upward  in  the  canal  until  it  reaches 
about  the  level  of  the  second  or  third  lumbar  vertebra.  The 
cord  presents  an  enlargement  in  the  cervical  region,  where 
the  branches  are  given  off  which  supply  the  upper  extremity  ; 
and  a  similar  enlargement  in  the  lower  lumbar  region,  where 
'he  branches  are  given  off  which  supply  the  lower  extremity. 
Of  course,  in  the  living  being,  its  curvature  corresponds  to  the! 
curvature  of  the  spinal  column. 

When  the  membranes  are  removed,  it  will    be  seen  that  the 

cord  presents  two   Median  Fissures,   one   Anterior,  and  one 

Posterior. 

z'       The  anterior  is  very  wide,  but  shallow;   w^hile  the,  ^posterior 

s  very  deep  and  narrow.     In  addition  to  these  two  fissures. 


THE  CENTRAL  NERVOUS  SYSTEM.  419 

the  spinal  nerves,  rising-  by  two  bundles  of  roots,  called  the 
anterior  and  posterior,  make  an  incomplete  and  irreg-ular  fissure, 
which  extends  throug-h  the  length  of  the  cord,  and  serves  to 
form  the  two  lateral  fissures.  Hence  it  will  be  seen  that  the 
cord  is  divided  into  an  anterior  column,  a  posterior  column,  and 
a  lateral  column,  the  last  being-  separated  from  the  other  two 
by  the  anterior  and  posterior  roots  of  the  spinal  nerves.  There 
are,  however,  other  columns  in  the  cord,  determined  more  by 
pathalog-ical  than  by  anatomical  examination. 

It  will  be  seen  that  the  cord,  unlike  the  brain,  is  arranged 
with  all  of  its  g'ray  matter  in  the  centre,  and  the  white  matter 
surrounding  it;  and  on  section  oE  the  cord  in  living-  animals 
deg-eneration  takes  place  in  two  directions.  Those  fibres  which 
convey  impulses  to  the  brain  deg-enerate  upward,  while  those 
which  convey  impulses  from  the  brain  deg-enerate  downward. 
These  pathological  changes  warrant  the  division  of  the  cord 
into  a  number  of  tracts,  not  noted  anatomically. 

As  in  all  portions  of  the  brain,  the  two  lateral  divisions  of 
the  cord,  separated  by  the  anterior  and  posterior  median  fis- 
sures, which  correspond  in  fact  to  the  great  longitudinal 
fissure  of  the  brain,  communicate  across  this  fissure  by  means 
of  commissural  fibres.  The  roots  of  the  spinal  nerves  extend 
through  the  white  matter  of  the  cord,  and  communicate  with 
the  gray  matter  in  its  interior.  This  gray  matter,  in  addition 
to  furnishing  trophic  centres,  contains  centres  which  act 
apparently  of  their  own  volition  without  stimulation  from  the 
brain.  As  a  matter  of  course  these  centres  are,  however, 
presided  over  by  the  brain,  and  can  be  restrained  in  their  action 
by  the  higher  centres. 

The  total  number  of  tracts  in  the  cord  is  large;  and  we  do 
not  find  the  corresponding  tracts  in  the  medulla,  but  in  many 
cases  two  or  more  tracts  are  blended  into  one  in  the  trans- 
mission from  the  cord  to  the  brain.  Commencing  at  the  ante- 
rior median  fissure  the  first  tract  is  called  the  Anterior  Pyramid ., 
or  Anterior  Pyramidal  Tract,  ■a.nA  next  to  this  is  found  the 
Anterior  Ground  Zone,  or  Anterior  Root  Zone,  being  that 
portion  of  the  cord  in  front  of  the  anterior  roots  of  the  spinal 


420  DESCRIPTIVE  ANATOMY. 

nerves.  Then  comes  behind  the  spinal  nerves  a  second  ground 
zone,  which  is,  however,  called  the  Lateral  bujidle,  and  external 
to  both  of  these  and  superficial  to  them  is  the  Antero-lateral 
tract,  v^^hich  conveys  both  ascending-  and  descending  fibres  to 
the  cerebrum.  Behind  this  tract,  also  on  the  superficial  sur- 
face of  the  cord,  is  the  Direct  Cerebellar  tract  which  extends 
as  far  as  the  posterior  root  zone;  and  between  the  direct  cere- 
bellar and  the  gray  matter  in  the  interior  of  the  cord  is  the 
Crossed  Pyramidal  Tract.  Behind  the  posterior  root  zone 
are  tw^o  tracts,  the  one  next  to  the  roots  of  the  nerves  being 
Burdacli  s  Column,  or  the  postero-lateral  column,  while  the 
one  next  to  the  postero-median  fissure  is  the  column  of  Goll, 
or  the  postero-median  column. 

When  these  columns  are  traced  upward  into  the  medulla,  it 
will  be  found  that  the  column  of  GoU  and  the  column  of  Bur- 
dach  unite  to  form  iho.  ^posterior  column  of  the  'medulla^  or,  as 
it  is  frequently  called,  funiculus  cuneatus  (Iv.  Dim.  of  funis, 
a  cord  ;  cuneatus,  wedge-shaped) ;  that  the  direct  cerebellar 
tract  passes  into  the  restiform  body  ;  that  the  crossed  pyram- 
idal and  the  direct  pyramidal  enter  into  the  anterior  pyramid 
of  the  medulla,  when  the  direct  pyramidal  will  pass  upward 
on  its  own  side,  while  the  crossed  pyramidal  passes  to  the  pos- 
terior side.  The  antero-lateral  or  ascending  and  descending 
cerebellar  tracts,  with  the  anterior  root  zone,  pass  upward 
into  the  lateral  column  of  the  medulla,  to  ascend  with  it  to 
form  the  central  fibres  of  the  pons  Varolii. 

In  addition  to  these  white  transmitting  fibres,  the  cord  con- 
tains in  its  interior  the  mass  of  gray  matter  before  alluded  to, 
which  is  arranged  like  the  letter  "H",  the  projections  in  front 
of  and  behind  the  cross-bar  of  the  "H"  being  called  the 
"horns." 

The  posterior  horns  are  long  and  slender,  while  the  ante- 
rior horns  are  bluntly  pointed.  These  masses  of  gray  matter 
contain  the  fibres  furnishing  the  various  centres  in  the  spinal 
cord. 

It  will  of  course  be  seen  that  the  branches  which  proceed 
from  the  spinal  cord  are  collectively  enormously  larger  than 


THE  CENTRAL  NERVOUS  SYSTEM.  421 

the  cord  itself,  and  it  can  be  readily  understood  that  large 
quantities  of  fibrous  tissue,  serve  in  a  measure  to  make  up  a 
portion  of  the  bulk  of  the  spinal  nerves. 

The  cord  is  nourished  by  the  blood  vessels  which  it 
carries  in  its  pia  matral  covering-  ;  and  these  blood  vessels 
are  derived  partly  from  the  anterior  and  posterior  branches 
of  the  vertebral  arteries,  and  partly  from  the  branches 
which  enter  the  spinal  canal  springing  from  the  intercostal 
and  lumbar  arteries. 

The  Spinal  Nerves. 

The  Spinal  nerves  consist  of  thirty-one  pairs,  which  taking 
their  origin  from  the  spinal  cord,  pass  outward  from  the  spi- 
nal canal  through  the  intervertebral  foramina,  and  are  distrib- 
uted throughout  the  body.  These  nerves  differ  materially 
from  the  cranial  nerves,  for,  whereas  the  latter  are  usually 
divided  into  separate  nerves,  having  motor,  general  sensory, 
or  special  sensory  functions,  the  spinal  nerves  are  composed 
of  bundles,  performing  all  nervous  functions.  Some  convey 
tactile  sensations,  some  painful,  some  motor,  and  some  various 
other  functions.  While  these  nerves  may  be  traced  into  the 
spinal  cord,  their  fibres  pass  through  the  various  columns  of 
the  cord  to  reach  different  portions  of  the  brain  ;  and  hence 
while  the  nerves  are  described  as  spinal  nerves  simply  from 
their  origin,  they  are  controlled  by  the  higher  centres  located 
in  the  cerebrum. 

They  differ  from  the  cranial  nerves  also  in  their  manner  of 
distribution.  The  cranial  nerves  pass  out  as  individual  nerves 
to  break  up  into  branches  distributed  to  various  portions  of 
the  head,  face,  and  viscera,  having  but  slight  communications 
with  one  another.  The  spinal  nerves  on  the  contrary  unite 
very  intimately  with  one  another  after  their  emergence  from 
the  spinal  column;  and  form  plexuses  from  which  branches  are 
given  off  to  carry  out  the  distribution  of  the  plexus.  There 
are  four  of  these  plexuses,  called  the  Cervical^  Brachial,  Lum- 
bar, and  Sacral.  Interposed  between  the  brachial  and  the 
the  lumbar  are  a  set  of  spinal  nerves,  the  Dorsal,  which  do 
not  unite  to  form   plexuses,  but  are  distributed   individually 


422  DESCRIPTIVE  ANATOMY. 

like  the  cranial  nerves.  Some  writers  mention  a  coccygfeal 
set  ;  but  these  in  reality  belong-  to  the  sacral  plexus. 

E)ach  spinal  nerve  as  itemerg-es  from  the  cord  is  surrounded 
by  a  prolongation  of  the  dura  mater,  which  lines  the  spinal 
canal  and  forms  a  sheath  for  the  nerve  as  far  as  the  interver- 
tebral foramen.  From  this  point  it  becomes  continuous  with 
the  ordinary  fibrous  sheath,  which  envelops  every  nerve,  and 
ceases  to  have  the  characteristics  of  the  dura  mater  lined  by  its 
arachnoid  membrane. 

Moreover  each  nerve  presents  upon  it  at  its  emerg^ence  an 
enlargement;  and  as  every  nerve  arises  by  an  anterior  and  a 
posterior  root,  this  enlargement,  or  ganglion,  is  confined  to  one 
of  these  roots.  The  posterior  root  of  a  spinal  nerve  conveys 
its  sensory  fibres,  while  the  anterior  root  conveys  the  motor 
fibres.  The  anterior  root  also  has  its  trophic  centre  situated 
in  the  spinal  cord,  so  that  cutting  that  nerve  causes  degenera- 
tion downward  into  the  nerve,  which  has  been  cut  loose  from 
its  trophic  centre,  while  cutting  the  posterior  root  between  the 
ganglion  and  the  cord  causes  degeneration  upward  into  the 
cord,  because  the  trophic  centre  is  located  in  the  ganglion  and 
not  in  the  cord. 

It  must  be  always  remembered  that  while  these  fibres  con- 
veying the  various  impulses  exist  in  the  spinal  nerves  they 
cannot  be  demonstrated  anatomically. 

E^ach  spinal  nerve  immediately  after  it  emerges  from  the 
spinal  canal  divides  into  an  anterior  and  a  posterior  branch. 
The  posterior  branches  are  small  in  size  and  comparatively 
unimportant.  They  convey  motor  and  sensory  impulses  to  the 
muscles  found  in  the  back  and  neck,  the  posterior  fibres  of  the 
sacral  plexus,  the  lowest,  conveying  impulses  to  the  lowest 
muscles  of  the  trunk,  while  the  limbs  are  supplied  entirely 
from  the  anterior  cords.  It  is  the  anterior  cords  which  enter 
into  the  formation  of  the  plexuses. 

The  Cervical  Plexus. 

The  first  plexus  formed  by  the  spinal  nerves  is  called  the 
Cervical.  It  Is  the  product  of  the  four  upper  cervical  nerves. 
The  plexus  is  formed  by  the  intercommunication  of  the  ante- 


THE  CENTRAL  NERVOUS  SYSTEM.  423 

rior  cords  of  these  four  cervical  nerves  ;  and  Is  found  opposite 
the  middle  of  the  sterno-cleido-mastoid  muscle.  Its  principal 
distribution  is  to  the  muscles  and  integfument  of  the  neck. 

The  plexus  itself  is  formed  in  the  following-  manner  :  The 
first  cervical  nerve  divides  into  an  anterior  and  a  posterior 
branch,  the  posterior  branch  forming-  what  is  known  as  the 
Great  Occipital  Nerve  {^Occipitalis  Major),  while  its  anterior 
division,  after  receiving  a  communication  from  the  eleventh 
and  twelfth  cranial  nerves,  sends  downward  a  communication 
to  the  second  cervical.  The  second  cervical,  after  g-iving-  oif  its 
posterior  branch,  sends  a  communication  to  the  third  and  the 
third  in  like  manner  sends  a  communicating-  branch  to  the  fourth, 
which  in  its  turn  sends  a  branch  to  the  fifth,  which  enters 
into  the  formation  of  the  brachial  plexus.  Prom  this  loosely 
formed  cervical  plexus  branches  are  g-iven  off  which  are  dis- 
tributed to  the  head,  face,  neck,  and  chest.  These  branches 
are,  for  convenience  of  study,  divided  into  two  sets,  superficial 
and  deep,  the  superficial  set  consisting-  of  three  named  branches, 
and  certain  unnamed  branches,  which  are  called  descending 
superficial  branches.  The  deep  set  consists  of  muscular 
branches. 

The  named  branches  of  the  superficial  set  are  the  Snperfi- 
cialis  Colli,  Auricularis  Mag'nus,  and  Occipitalis  Minor. 

Superficial  Branches. 

Superficialis  Colli       Auricularis  Mag-nus      Occipitalis  Minor 
The  Superficialis  Colli. 

The  Superficialis  Colli,  the  first  branch,  is  the  product  of 
the  sccotzd  and  third  cervical  nerves  ;  and  like  all  the  superfi- 
cial branches  from  this  plexus,  it  winds  around  the  posterior 
border  of  the  sterno-cleido-mastoid  muscle,  about  at  its  middle, 
and  becomes  superficial  in  that  situation.  It  then  passes  up- 
ward and  forward,  crosses  the  sterno-cleido-mastoid,  runs  to 
the  lower  border  of  the  inferior  maxilla,  and  spreads  out  into 
a  fan-shaped  set  of  twigs,  which,  after  communicating-  with 
the  facial  nerve,  are  distributed  to  the  skin  covering  the  lateral 
aspect  of  the  face. 


424  DESCRIPTIVE  ANATOMY. 


The  Auricularis  Magnus. 

The  Auricularis  Magnus  is  the  product  of  the  second  and 
third  cervical  nerves.  After  emerg-ing-  from  the  posterior  bor- 
der of  the  sterno-cleido-mastoid,  it  crosses  that  muscle,  and 
divides  into  two  branches,  mastoid  and  auricular. 

The  mastoid  branch  ascends  to  the  mastoid  process  of  the 
temporal  bone  and  is  distributed  to  the  skin  in  that  reg"ion  after 
communicating"  with  the  seventh  nerve. 

The  auricular  branch  divides  into  several  twig^s,  which  are 
distributed  to  the  skin  on  the  back  of  the  pinna. 

The  Occipitalis  Minor. 

The  Occipitalis  Minor  is  derived  from  the  second  cervical 
nerve.  It  passes  upward  nearly  parallel  with  the  posterior 
border  of  the  sterno-cleido-mastoid  muscle;  and  gives  off  three 
sets  of  branches,  one  passing-  to  the  back  of  the  ear,  one  over 
the  mastoid  process  of  the  temporal,  where  it  communicates 
with  the  auricularis  magnus,  and  the  third,  the  larg-est,  passing 
to  the  occipital  bone,  where  it  runs  over  the  occipito-frontalis 
muscle,  and  is  distributed  to  it  and  to  the  skin  covering  the 
occipital  bone. 

The  Descending  Superficial  Branches. 

The  unnamed  Descending-  Superficial  Branches  are  produced 
by  the  third  -dM^^  fourth  cervical  nerves.  They  emerg-e  from 
beneath  the  sterno-cleido-mastoid  muscle,  like  the  preceding 
branches,  about  opposite  the  middle  of  its  posterior  border- 
They  are  irregular  in  size  and  number.  One  set  passes  down- 
ward and  inward  toward  the  mid-line  of  the  body,  crossing 
the  clavicle  near  its  inner  extremity  and  ending  in  the  integu- 
ment which  covers  the  front  of  the  thorax.  The  second  set 
passes  nearly  vertically  downward,  to  cross  the  middle  of  the 
clavicle,  and  be  distributed  to  the  integ-ument  covering  the 
pectoral  muscles,  while  the  third  set,  called  sometimes  the 
acromial,  or  deltoid,  passes  outzvard,  and  is  distributed  to  the 
skin  in  the  neig-hborhood  of  the  shoulder. 


THE  CENTRAL  NERVOUS  SYSTEM.  425 


Deep  Branches. 

Muscular  Phrenic 

Communicans  Noni 

The  Muscular  Branches. 

The  muscular  branches  are  distributed  to  all  of  the  muscles 
of  the  front  of  the  neck  with  the  exception  of  the  depressors 
of  the  hyoid  bone.  They  consist  of  a  branch  to  the  sterno- 
cleido-mastoid  muscle,  which  arises  from  the  second  cervical 
and  communicates  with  the  eleventh  cranial  in  the  substance 
of  the  sterno-raastoid  muscle  ;  a  branch  to  the  scalenus  medius, 
coming-  from  the  third  ^nA  fourth  nerves  ;  one  to  the  levator 
anguli  scapulas  ;  and  several  branches  to  the  trapezius,  which 
are  the  product  of  the  third  and  fourth  cervical  nerves  and 
which  communicate  with  one  another. 

Besides  this,  there  are  some  branches,  sometimes  described 
as  internal,  which  supply  the  rectus  capitis  lateralis,  the  rec- 
tus capitis  anticus  minor,  and  the  long-us  colli. 

The  Communicans  Noni. 

The  most  important  communicating  branch  is  the  Commu- 
nicans Noni.  This  nerve  is  the  product  of  the  second  and 
third  cervical  nerves.  It  passes  downward,  forward,  and 
inward,  and  unites  with  the  descending-  branch  of  the  hypo- 
g-lossal  on  the  front  of  the  common  carotid  artery,  immediately 
above  the  point  at  which  the  omo-hyoid  crosses  that  vessel. 
After  this  communication  it  passes  with  the  descendens  noni 
to  be  distributed  to  the  muscles  of  the  infra-hyoid  group,  or 
depressors  of  the  hyoid  bone,  with  the  exception  of  the  thyro- 
hyoid, which   is  supplied   by  a  branch   from  the   hypog-lossal 

nerve  itself. 

The  Phrenic. 

The  last  and  most  important  branch  of  the  plexus  is  the 
l^hrenic  Nerve.  It  is  formed  by  contributions  from  the  third 
and  fourth  cervical  nerves,  reinforced  by  a  small  filament  from 
the  fifth.  The  course  of  the  nerve  on  the  two  sides  of  the 
hody  differs. 


426  DESCRIPTIVE  ANATOMY. 

On  the  rig-ht  side  it  descends  on  the  front  of  the  scalenus 
anticus  muscle,  reaches  the  inner  side  of  that  muscle  just  be- 
fore it  crosses  the  subclavian  artery,  drops  off  to  the  inner  side, 
and  becomes  an  anterior  relation  of  the  first  portion  of  the 
subclavian,  thoug-h  occasionally  it  remains  on  the  scalenus 
anticus  until  after  it  has  passed  the  artery.  It  then  runs  in  the 
interval  between  the  subclavian  artery  and  vein,  continues  its 
downward  course  into  the  thorax,  lying-  to  the  outer  side  of  the 
right  vena  innominata  and  then  the  superior  vena  cava,  passes 
in  front  of  the  root  of  the  right  lung,  then  lies  on  the  pericardium 
between  it  and  the  right  pleura,  and  finally  pierces  the  dia- 
phragm, and  is  distributed  to  that  muscle  from  its  under 
surface. 

The  left nerve,  formed  in  the  same  way,  passes  on  the  scalenus 
anticus  muscle  to  cross  over  the  front  of  the  first  portion  of  the 
subclavian,  then  to  descend  in  front  of  that  vessel  and  opposite 
the  interval  between  it  and  the  left  common  carotid,  lying  to 
the  outer  side  and  in  front  of  the  pneumogastric  nerve.  Then 
it  crosses  the  end  of  the  transverse  aorta,  passes  downward  on 
the  left  side  of  the  pericardium,  lying  next  to  the  left  pleura, 
and  then,  like  its  fellow  of  the  opposite  side,  enters  the  dia- 
phragm and  is  distributed  to  it  from  its  under  surface. 

The  Brachial  Plexus. 

The  Brachial  Plexus  is  the  second  great  plexus  formed  by  the 
anterior  cords  of  the  cervical  nerves.  It  is  the  result  of  inter- 
communications between  the  four  lozuer  cervical  nerves  and 
a  portion  of  the  first  dorsal  nerve.  The  manner  of  its  forma- 
tion differs  indifferent  individuals;  but  it  is  usually  formed  ia 
the  following  way:  The  fifth  and  sixth  cervical  nerves  unite 
to  form  a  single  cord;  the  eighth  cervical  and  the  first  dorsal 
unite  to  form  one  cord,  while  the  seventh  cersiical  passes  out 
alone.  Then  the  seventh  unites  with  the  cord  formed  by  the 
fifth  and  sixth,  so  that  at  one  time  there  are  but  two  cords  in 
the  plexus,  one  resulting  from  the  union  of  the  fifth  and  sixth 
with  the  seventh,  and  the  other  formed  by  the  eighth  cervical 
with  the  first  dorsal.  Shortly  after,  however,  each  of  these 
two  cords  gives  off  a  branch;  and  these  branches  unite  to  form 


THE  CENTRAL  NERVOUS  SYSTEM.  427 

a  third  cord  in  the  plexus,  this  middle  cord  being  the  product 
of  all  of  the  cords  which  enter  into  the  formation  of  the  brachial 
plexus. 

The  plexus  is  triang-ular  in  outline,  with  its  base  directed  to- 
wards the  spinal  column  and  its  apex  extending- downw^ard. back- 
ward and  outward  towards  the  axillary  space.  It  passes  between 
the  scaleni  muscles  ;  and  comes  into  relationship  with  the  sub- 
clavian artery  in  the  second  portion  of  its  course.  Here  most 
of  the  cords  lie  above  that  vessel  ;  but  the  branch  derived 
from  the  dorsal  nerve  lies  behind  it.  In  the  third  portion  of 
the  subclavian  artery  the  plexus  lies  above  and  to  the  outer 
side  ;  but  on  a  plane  posterior  to  it.  It  then  continues  forward 
and  outward,  coming  into  relationship  with  the  axillary  artery, 
and  lies  first  to  its  outer  side  ;  but  in  the  second  portion  of  that 
vessel  ;  viz.,  that  part  behind  the  pectoralis  minor  muscle  ,the 
plexus  consists  of  three  cords,  one  to  the  inner  side,  one  to  the 
outer  side,  and  one  lying  behind  the  axillary  artery.  Just  at  the 
termination  of  the  second  portion  the  inner  and  the  outer  cord 
each  give  off  a  branch  ;  and  the  two  branches  formed  in  this 
manner  unite  to  form  the  median  nerve,  so  that,  on  a  line  drawn 
from  the  tip  of  the  coracoid  process  of  the  scapula  downward 
and  inward  to  the  lower  part  of  the  third  intercostal  space,  it 
will  be  seen  that  the  axillary  artery  is  completely  surrounded 
by  the  cords  of  the  plexns.  The  outer  and  inner  cords  lie  on 
the  outer  and  inner  sides  of  the  artery,  the  posterior  cord 
behind  it,  and  the  branches  which  form  the  median  nerve  lie 
upon  its  front. 

Immediately  after  the  formation  of  the  median,  that  nerve 
drops  to  the  outer  side  of  the  axillary  artery,  and  maintains 
that  relation  to  the  termination  of  that  vessel,  while  the  re- 
maining cords  of  the  plexus  break  np  into  their  terminal 
h)  ranches. 

Branches  of  the  Brachial  Plexus. 

The  distribution  of  the  brachial  plexus  is  chiefly  to  the 
upper  extremity,  supplying  the  muscles  and  integument ;  but 
before  reaching  its  point  of  termination  it  gives  oflf  way-side 
branches,  some   muscular  and  some  cutaneous,  which  are  dis- 


428 


DESCRIPTIVE  AX  ATOMY 


tributed  to  the  lateral  aspect  of  the  chest,  as  well  as  to   the 
muscles  of  the   scapular   group  and  the   skin  covering*  them. 


Wayside  Branches. 


Above  the 
Clavicle 


f  Suprascapular 
Rhomboid 
Posterior    Tho- 
racic 
Communicating- 
Subclavian 
Scaleni 
lyong-us  Colli 


Below  the 

Clavicle 


Anterior  Tho- 
racic, internal. 

Anterior  Tho- 
racic, external. 

SubscaDular 


The  Suprascapular. 

The  Siiprasca^idar  hrancJi  is  derived  from  the  fifth  and 
sixth  cervical  nerves.  It  passes  downward  and  outward  par- 
allel with  the  posterior  belly  of  the  omo-hyoid  muscle.  Reach- 
ing" the  upper  border  of  the  scapular  it  passes  throug-h  the 
suprascapular  notch  beneath  the  transverse  lig-ament.  and 
consequently  below  the  corresponding-  artery,  enters  the 
supraspinatus  muscle,  gives  motor  fibres  to  that  muscle  and 
a  twig-  to  the  shoulder  joint,  while  the  remaining-  portion  of 
the  nerve  passes  around  the  anterior  border  of  the  spine  of  the 
scapular  to  be  distributed  to  the  infraspinatus  muscle. 

The  Rhomboid. 

The  branch  to  the  Rhomboideus  is  a  product  of  the  nftli 
cervical  nerve.  It  passes  throug-h  the  fibres  of  the  scalenus 
medius,  and  is  then  distributed  to  the  rhomboid  muscle,  or 
muscles. 

The  Posterior  Thoracic. 

The  Posterior  Thoracic,  or  External  Respiratory  Nerve  of 
Bell,  is  the  product  of  the  fifth,  sixth,  and  seventh  nerves.  It 
passes  downward  behind  the  brachial  plexus  and  the  first  por- 
tion of  the  axillar\^  and  is  distributed  to  the  serratus  mag-nus 
muscle. 

Communicating. 

The  communication  with  the  cervicle  plexus  is  by  means  of 
the  fifth  cervical,  which  joins  with  the  phrenic  nerve. 


THE  CENTRAL  NERVOUS  SYSTEM.  429 

The  Subclavian. 

The  nerve  to  the  Subclaviiis  jiiuscle  is  a  slender  twig*,  which 
is  derived  from  the  fifth  cervical,  and  crosses  the  front  of  the 
third  portion  of  the  subclavian  artery  to  enter  the  subclavius 
muscle. 

The  Branches  g-iven  below  the  clavicle,  besides  the  terminal 
ones,  are  the  external  and  internal  anterior  thoracic  and  the 
subscapular  nerves. 

The  External  Anterior  Thoracic. 

The  Exteriial  Anterior  Thoracic,  derived  from  the  outer 
cord  of  the  plexus,  is  distributed  to  the  pectoralis  major  muscle. 

The  Internal  Anterior  Thoracic. 

The  Internal  Anterior  Thoracic,  the  product  of  the  inner 
cord,  passes  between  the  first  portion  of  the  axillary  artery  and 
its  vein,  occasionally  perforating-  the  vein  itself;  and  after  re- 
ceiving- a  communication  from  the  external  anterior  thoracic, 
is  distributed  to  the  pectoralis  major. /or^ 

The  Subscapular. 

The  Subscapular  nerves  are  three  in  number  ;  and  the}''  are 
derived  from  the  posterior  cord.  They  are  known  as  the 
upper,  middle,  and  lower.  The  upper  is  distributed  to  the 
subscapularis  muscle  alone,  the  middle  accompanies  the  sub- 
scapular artery,  and  terminates  near  the  latissimus  dorsi  ; 
while  the /oz.'cr  is  distributed  to  the  teres  major,  furnishing" 
some  twig-s  to  the  subscapularis. 

Terminal  Branches. 

Musculo-cutaneous  Internal  Cutaneous 

Median  Lesser  Internal  Cutaneous 

Ulnar  Musculo-Spiral 

Circumflex 

The  terminal  branches  of  the  Brachial  Plexus  orig-inate  from 
the  cords  of  the  plexus  as  follows  :  The  internal  cord  produces 
the  internal  cutaneous,  the  lesser  internal  cutaneous,  the  ulnar, 


430  DESCRIPTIVE  ANATOMY. 

and  one  head  of  the  median.  The  externcd  cord  divides  into 
two  branches  :  one  forms  the  outer  head  of  the  median,  while 
the  other  is  the  musculo-cutaneous.  The  -posterior  cord  di- 
vides into  the  circumflex  and  the  musculo-spiral. 

The  division  of  the  plexus  takes  place  on  the  beg-inniag-  of  the 
third  portion  of  the  axillary  artery,  which  is  here  completely 
surrounded  by  the  cords  of  the  plexus;  but  immediatelvaf  ter  the 
formation  of  the  median,  that  nerve  drops  to  the  outer  side  of 
the  axillary  artery;  and  the  relation  is  then,  median  and  musculo- 
cutaneous to  the  outer  side,  internal  and  lesser  internal  cuta- 
neous and  ulnar  nerves  to  the  inner  side,  musculo-spiral  be- 
hind, and  circumflex  behind  as  far  as  the  interval  between  the 
teres  major  and  lower  border  of  the  subscapularis,  where  it 
passes  to  the  back  of  the  humerus  and  ceases  to  be  a  relation. 

The  Musculo-Cutaneous. 

The  Musculo-cutaneous  Nerve,  the  product  of  the  outer  cord  of 
the  brachial  plexus,  receives  fibres  which  can  be  traced  to  the 
fifth,  sixth,  and  seventh  nerves,  passes  downward  as  an 
external  relation  of  the  third  portion  of  the  axillary  artery 
until  it  reaches  the  coraco-brachialis  muscle.  It  then  passes 
through  the  substance  of  that  muscle,  supplying*  the  muscle 
with  branches  as  it  is  transmitted  through  it.  E^merging 
from  the  coraco-brachialis,  it  passes  between  the  brachialis 
anticus  and  the  biceps,  runs  into  the  interval  between  the  brachi- 
alis anticus  and  the  supinator  longus,  where  it  becomes  superfi- 
cial a  little  above  the  elbow  joint,  and  passing  across  the  outer 
front  aspect  of  that  joint,  divides  into  two  branches.  The 
-posterior  branch  passes  downward  and  backward;  and  is 
distributed  to  the  skin  on  the  postero-external  aspect  of  the 
forearm  as  far  as  the  wrist.  The  anterior  branch,  supplying 
the  integument  on  the  antero-external  face  of  the  forearm, 
communicates  with  the  radial  nerve  near  the  wrist,  and  extends 
as  far  as  the  skin  covering  the  thenar  eminence. 

The  nerve  in  its  course  gives  off  muscular  branches  to  the 
coraco-brachialis,  the  biceps,  and  the  inner  portion  of  the 
brachialis  anticus. 


THE  CENTRAL  NERVOUS  SYSTEM.  431 


The  Internal  Cutaneous. 

The  Internal  Cutaneous  Nerve  is  the  product  of  the  inner 
cord  of  the  plexus  ;  and  is  probably  derived  from  the  eiofhth 
cervical  and  first  dorsal.  It  is  an  internal  relation  of  the  third 
portion  of  the  axillary  arter}^  to  the  termination  of  that  vessel  ; 
and  then  becomes  an  antero-internal  relation  to  the  brachial 
artery,  lying-  in  close  companionship  to  the  basilic  vein. 
At  the  middle  of  the  brachial  artery  the  nerve,  with  the  basi- 
lic vein,  pierces  the  investing-  fascia  ;  and  still  remaining*  an 
antero-internal  relation  of  the  brachial  artery  to  its  termina- 
tion, is,  for  its  lower  half,  separated  from  that  vessel  by  the 
deep  fascia  of  the  forearm. 

At  the  elbow-joint  it  breaks  up  into  branches,  some  of 
which,  lying  on  the  front  of  the  bicipital  fascia,  are  anterior 
relations  of  the  brachial  artery,  but  separated  from  it  by  this 
fascia.  The  remaining  branches  continue  their  course  down- 
ward, being  divided  into  an  anterior  and  a  posterior  set.  the 
anterior  supplying  the  integ-ument  of  the  inner  front  aspect  of 
the  forearm  as  far  as  the  wrist,  while  the  ^o^/'t'r/or  supply  the 
integument  on  the  postero-internal  aspect  of  the  forearm  down 
to  the  wrist. 

The  Lesser  Internal  Cutaneous. 

The  Lesser  Inter)ial  Cutaneous^  or  Nerve  of  Wrisberg,  aris- 
ing from  the  internal  cord,  receives  its  branches  from  the 
eighth  cervical  and  first  dorsal.  It  is  very  irregular  in  its 
origin,  and  ma}'  be  the  product  of  the  lateral  cutaneous  branch 
of  the  second  intercostal  nerve  ;  but,  as  a  rule,  it  simply  re- 
ceives a  communication  from  that  nerve.  At  first  it  is  an 
internal  relation  of  the  axillary  artery,  and  is  separated  from 
that  artery  by  the  axillary  vein.  It  continues  downward,  too 
distant  to  be  considered  a  relation  of  the  brachial  artery,  to 
thj  postero-internal  aspect  of  the  arm,  and  near  the  elbow 
turns  backward  to  be  distributed  to  the  integ-ument  on  the 
1  jwer  third  of  the  arm  and  in  the  neig-hborhood  of  the  olecra- 
non process. 


432  DESCRIPTIVE  ANATOMY. 

The  Ulnar. 

The  Ulnar  Nerve  is  the  last  branch  of  the  internal  cord  of 
tHe  plexus;  and  like  the  preceding-  branches,  contains  fibres 
from  the  eigfhth  cervicle  and  first  dorsal  nerves.  It  is  first  an 
internal  relation  of  the  axillary  artery,  lying-  between  it  and  the 
lesser  internal  cutaneous  nerve.  It  then  becomes  an  internal 
relation  of  the  brachial  for  the  upper  half  of  the  course  of  that 
vessel;  and  at  the  middle  of  this  artery  it  reaches  the  inferior 
profunda  branch  of  the  brachial.  Accompanied  by  this  latter 
branch,  it  passes  backward,  pierces  the  internal  inter-muscular 
septum,  and  runs  to  the  space  between  the  internal  condyle  of 
the  humerus  and  the  olecranon  process  of  the  ulnar,  forming'^^ 
what  is  g-enerally  known  as  the  "funny  bone".  The  nerve 
then  passes  between  the  two  heads  of  the  flexor  carpi  ulnaris 
muscle;  and  at  the  junction  of  the  upper  third  with  the  lower 
two-thirds  of  the  forearm  it  becomes  an  internal  relation  of  the 
ulnar  artery.  It  then  passes  downward,  lying-  on  the  fibres  of 
the  flexor  profundus  digitorum,  and  maintains  a  continuous 
internal  relation  to  the  ulnar  artery  to  the  wrist  joint.  At 
this  point  it  becomes  superficial  to  the  anterior  annular  liga- 
ment, passes  to  the  outer  side  of  the  pisiform  bone,  and  enters 
the  palm  of  the  hand,  where  it  divides  into  a  superficial  and  a 
deep  branch. 

In  the  commencement  of  its  course  the  nerve  lies  on  the  an- 
terior face  of  the  internal  inter-muscular  septum.  At  the 
middle  of  the  arm  it  pierces  this  septum,  and  passes  downward 
in  the  fibres  of  the  triceps  muscle,  then  behind  the  internal 
condyle  of  the  humerus,  then  between  the  two  heads  of  the  flexor 
carpi  ulnaris,  separated  from  the  ulnar  artery  for  the  upper 
third  of  the  course  of  that  vessel.  Then  the  nerve  lies  with 
the  flexor  carpi  ulnaris  to  its  inner  front  side,  and  the  flexor 
profundus  digitorum  behind  it,  and  with  the  ulnar  artery  to 
its  outer  side  for  the  lower  two-thirds  of  its  course. 

The  nerve  gives  off  no  branches  until  after  it  has  passed  the 
elbow  joint,  where  it  supplies  muscular  branches  to  the  flexor 
carpi  ulnaris  and  the  inner  half  of  the  flexor  profundus  digfi- 
torum.     About  three  inches  above  the  wrist  joint  it  g-ives  off  a 


THE  CENTRAL  NERVOUS  SYSTEM.  433 

cutaneous  branch,  the  dorsal  cutaneous  branch  of  the  Ulnar, 
which  will  be  described  later  ;  and  then  a  superficial  branch 
which  enters  the  palm  of  the  hand.  A  few  small  twig's  are 
given  olT  to  the  elbow  joint. 

Superficial  Branch.  After  entering-  the  palm,  the  super- 
ficial branch  supplies  the  palmaris  brevis,  and  the  skin  cover- 
ing the  hypothenar  eminence,  a  twig  to  the  inner  side  of  the 
little  finger,  and  a  branch  which  bifurcates  to  supply  the  ad- 
jacent sides  of  the  little  and  ring  fingers,  and  lastly  a  commu- 
nicating branch  to  the  median  nerve. 

The  distribution  of  the  collateral  digital  branches  to  the 
fingers  is  accomplished  by  the  median  and  ulnar  nerves.  These 
branches  pass  to  the  clefts  between  the  fingers,  divide  into  two, 
which  course  along  superficial  to  the  corresponding  arteries,  and 
opposite  the  posterior  extremity  of  the  nail  send  dorsal  branches 
around  which  ramify  between  the  nail  and  its  matrix,  each 
nerve  communicating  with  its  fellow  of  the  opposite  side  around 
both  the  palmar  and  the  dorsal  aspects.  The  ulnar  nerve  sup- 
plies the  little  finger  and  the  inner  side  of  the  ring  finger. 

Deep  Branch.  The  Deep  Branch  of  the  Ulnar  passes  be- 
tween the  flexor  minimi  digiti  and  the  abductor  minimi  digiti, 
runs  along  the  palm  of  the  hand  accompanying  the  deep  palmar 
arch,  supplies  the  two  inner  lumbrical  muscles,  the  two  outer 
interosseous  muscles,  the  muscles  of  the  hypothenar  eminence, 
with  the  exception  of  the  palmaris  brevis,  and  in  the  thenar 
group,  supplies  one  muscle  and  a  half,  viz.,  the  adductor  poUi- 
cis,  and  the  deep  head  of  the  flexor  brevis  pollicis,  the  remaining 
portion  of  the  hand  being  supplied  by  the  median  nerve. 

The  Dorsal  Ciilancoiis  Branch  of  the  Ulnar  arises  three 
inches  above  the  wrist  joint,  passes  to  the  back  of  the 
forearm,  and  descends  behind  the  styloid  process  of  the  ulnar 
to  the  back  of  the  hand.  Here  it  divides  into  cutaneous 
branches,  the  most  internal  of  which  is  distributed  to  the 
ulnar  side  of  the  little  finger.  The  second  passes  to  the 
cleft  between  the  little  and  ring  fingers,  where  it  divides  into 
dorsal  collateral  digital  branches  for  these  two  fingers.  The 
third  cutaneous  /jranch  communicates  with  a  branch  from  the 
radial  nerve,  passes  to  the  cleft  between  the  ring  and  middle 

Des  Anat— 28 


434  DESCRIPTIVE  ANATOMY. 

fing"ers,  and  divides  to  supply  the  adjacent  sides  of  these  two 
fing-ers.  These  dorsal  collateral  digfital  branches  communicate 
in  the  matrix  of  the  nail  with  the  palmar  branches  already 
noticed. 

The  Median. 
The  Median  Nerve  is  the  joint  product  of  the  internal  and 
external  cords  of  the  brachial  plexus  ;  and  derives  fibres  from 
all  of  the  anterior  cords  entering-  into  the  formation  of  that 
plexus.     It  is  formed  at  the  commencement  of  the  third  por- 
tion of  the  axillary  artery  by  the  junction  of  a   branch   from 
the  inner  with  a  corresponding*  branch  from  the  outer  cord  of 
the  plexus.     Formed  on  the  front  of  the  third  portion  of  the 
axillary  artery,  it  immediately   drops  to  its   outer   side,    and 
maintains   that   relation  to  the  termination   of   the  vessel.     It 
then  becomes  an  outer  relation  of  the  brachial  artery,  lying- 
between  that  artery  and  the  coraco-brachialis  muscle.     About 
opposite  the  insertion  of  the  coraco-brachialis  it  passes  to  the 
front  of  the  brachial  artery,  crossing-  it  very  obliquely,  so  as 
to  remain  on  the  front  of  that  vessel  for  the  middle  one-third 
of  its  course.     It  then  drops  to  the  inner  side  of  the  brachial 
artery,  and  maintains  that  relation  to  the  termination  of  that 
vessel,  a  fing-er's  breadth  below  the  middle  of  the  front  of  the 
elbow  joint.     It  should  here  be  noted  that  in  cases  of  hig-h 
bifurcation  of  the  brachial,  the  median  nerve  almost  invariably 
passes  between  the  two  branches,  the  branch  in  front  usually 
corresponding-  to  the  radial  artery,  and  the  branch  behind  to 
the  ulnar.     In   some  cases  the   median   nerve   passes   behind 
instead  of  in  front  of  the  brachial  artery. 

Reaching-  the  elbow  joint  it  lies  in  the  triangular  space,  the 
base  of  which  is  directed  upward,  and  is  formed  by  a  line 
drawn  from  the  inner  to  the  outer  condyle  of  the  humerus,  th 
external  boundary  being-  the  supinator  long-us  and  the  innei 
boundary  the  pronator  radii  teres.  The  nerve  exactly  bisects 
this  space,  passes  between  the  two  heads  of  the  pronator  radi' 
teres  muscle,  the  deep  head  of  which  alone  separates  it  from 
the  ulnar  artery.  Crossing-  over  the  ulnar  artery,  and  sep- 
arated from  it  by  the  deep  head  of  this  muscle,  it  then  passes 
down  the  middle  of  the   front  of  the  forearm,  covered  by  the 


THE  CENTRAL  NERVOUS  SYSTEM.  435 

superficial  head  of  the  pronator  radii  teres  and  overlapped  by 
the  flexor  carpi  radialis  on  its  outer  side  and  the  flexor  sublimis 
dig"itorura  on  its  inner  side,  and  lying-  nearly  directly  behind 
the  palmaris  long-us.  It  then  passes  to  the  front  of  the  wrist 
joint,  crosses  beneath  the  anterior  annular  lig-ament  into  the 
palm  of  the   hand,   and  breaks  up  into  its  terminal   branches. 

Like  the  ulnar  nerve  it  g-ives  off  no  branches  in  the  arm. 
It  gives  off  a  few  small  branches  to  the  elbow  joint ;  and  just 
below  the  bend  of  the  elbow  g*ives  off  a  large  branch,  called 
the  anterior  interosseous. 

The  Anterior  Interosseous  Nerve  arises  opposite  the  bicipi- 
tal tubercle  of  the  radius,  runs  downward  on  the  interosseous 
membrane,  accompanied  by  the  anterior  interosseous  artery, 
as  far  as  the  upper  border  of  the  pronator  quadratus  muscle, 
where  after  giving-  branches  to  the  deep  surface  of  that  muscle, 
it  pierces  the  interosseous  membrane  and  communicates  with 
the  posterior  interosseous  nerve. 

Immediately  below  the  elbow  joint  the  median  gives  off 
branches  to  all  of  the  muscles  on  the  front  of  the  forearm  with 
the  exception  of  the  flexor  carpi  ulnaris  and  the  inner  half  of 
the  flexor  profundus  digitorum.  In  other  words,  it  supplies 
muscular  twig-s  to  six  and  one-half  out  of  eig-ht  of  the  muscles 
of  the  forearm  ;  viz.,  the  pronator  radii  teres,  flexor  carpi  radi- 
alis, palmaris  long-us,  flexor  sublimis  digitorum,  flexor  long-us 
pollicis,  pronator  quadratus,  and  outer  one-half  of  the  flexor 
profundus  digitorum. 

Just  before  reaching-  the  anterior  annular  ligament  it  gives 
off  cutaneous  branches,  which  are  distributed  to  the  integument 
covering-  the  thenar  eminence  of  muscles,  and  which  commu- 
nicate with  the  superficial  branch  of  the  ulnar  nerve,  distrib- 
uted to  the  hypothenar  eminence. 

The  remaining  branches  are  divided  into  two  sets.  The 
first  set  supplies  the  superficial  muscles  of  the  thenar  eminence, 
the  abductor  pollicis,  the  flexor  ossis  metacarpi  pollicis,  and 
the  superficial  head  of  the  flexor  brevis  pollicis  ;  or,  in  other 
words,  all  of  the  muscles  which  arise  from  the  trapezium  and 
the  anterior  annular  lig-ament,  the  remaining-  muscles  of  the 
group   being   supplied   by   the   ulnar    nerve.     The  other  set 


436  DESCRIPTIVE    ANATOMY. 

divides  into  palmar  collateral  branches,  of  which  thejii'st  tvjo 
pass,  one  to  the  radial  and  the  other  to  the  ulnar  side  of  the 
thumb  on  its  palmar  aspect,  communicating-  with  one  another 
and  with  dorsal  cutaneous  branches,  w^hich  will  be  described 
later.  The  third  hi'anch  passes  to  the  radial  side  of  the  index 
finger  ;  Va'^  fourth  to  the  cleft  between  the  index  and  middle 
fingers  :  and  the  fifths  after  receiving  a  communication  from 
the  ulnar,  passes  to  the  cleft  between  the  middle  and  ring 
fingers,  and  supplies  the  adjacent  sides  of  those  fingers,  all 
of  these  branches  communicating  with  one  another  and  also 
with  the  dorsal  nerves. 

The  Musculo-Spiral. 

The  Musculo- S;piral,ih.&  largest  branch  of  the  brachial  plexus, 
arises  from  the  posterior  cord  ;  and  is  said  by  some  authorities 
to  get  fibres  from  all  of  the  cords  of  the  brachial  plexus, 
though  others  deny  that  it  receives  any  from  the  fifth  cervical 
nerve.  It  passes  downward  as  a  posterior  relation  of  the  third 
portion  of  the  axillary  artery.  At  the  termination  of  that 
vessel  it  passes  between  the  internal  head  of  the  triceps  muscle 
and  the  shaft  of  the  humerus ;  and  at  the  junction  of  the 
lower  third  with  the  upper  two  thirds  of  the  shaft  of  the 
humerus,  pierces  the  external  intermuscular  septum,  and 
appears  opposite  the  interval  between  the  brachialis  anticus 
and  the  supinator  longus.  At  the  elbow  joint,  while  still  ly- 
ing between  these  two  muscles,  it  divides  into  its  two  terminal 
branches,  the  radial  and  the  ^posterior  iyiterosseus.  Before 
its  division  it  gives  off  both  cutaneous  aud  muscular  branches. 

Branches  of  the  Musculo-Spiral. 


Way- 
Side 


(  Internal  |  Radial 

Cutaneous  K  Upper  Kxternal  Terminal  ■(  Posterior 

(  Lower  E^xternal  (  Interosse 
Muscular 

The  Internal  Cutaneous  B7'anch  is  distributed  to  the  skin 
covering  the  middle  of  the  back  of  the  arm  ;  and  extends 
as  far  as  the  distribution  of  the  nerve  of  Wrisberg,  with  which 
it  communicates. 

The  Upper  External  Cutaneous  pierces  the  external  inter- 


THE  CENTRAL  NERVOUS  SYSTEM.  437 

muscular  septum  ;  and  is  distributed  to  the  skin  covering"  the 
outer  portion  of  the  biceps  muscle. 

The  Lo'.ver  External  Cutaneous  Branch  pierces  the  exter- 
nal intermuscular  septum  ;  and  is  distributed  to  the  skin  cov- 
ering- the  supinator  longus  muscle,  lying-  in  the  interval 
between  the  musculo-cutaneous  nerve  on  its  outer  side,  and  the 
posterior  branch  of  the  internal  cutaneous,  on  its  inner  side. 

The  Muscular  Branches  are  distributed  to  the  three  heads 
of  the  triceps  muscle,  a  branch  to  the  anconeous,  which  is  a 
continuation  of  the  triceps,  to  the  brachialis  anticus,  supinator 
longus,  and  extensor  carpi  radialis  long-ior,  that  is,  to  all  of 
the  muscles  which  take  their  orig-in  above  the  external  con- 
dyle of  the  humerus. 

The  Radial. 

Of  the  two  terminal  branches  of  the  median,  the  Radial  is 
purely  a  nerve  of  common  sensation.  It  commences  in  the 
interval  between  the  supinator  long-us,  externally,  and  the 
brachialis  anticus,  internally.  It  then  passes  downward  ;  and 
in  the  upper  part  of  its  course  is  a  distant  external  relation  to 
the  radial  artery.  In  the  middle  third  it  is  a  close  external  re- 
lation of  that  vessel ;  but  at  the  junction  of  the  middle  and  lower 
thirds  of  the  radius  it  passes  beneath  the  tendon  of  the  supinator 
longus  and  appears  upon  the  back  of  the  forearm,  ceasing  to 
be  a  relation  of  its  artery.  Emerg-ing  from  beneath  this  tendon, 
it  becomes  superficial,  g-ives  a  branch  which  divides  to  supply 
the  radial  and  ulnar  sides  of  the  thumb  on  their  dorsal  aspect, 
a  second  branch  to  the  radial  side  of  the  index  fingfer,  a  third, 
which  divides  to  supply  the  adjacent  sides  of  the  middle  and 
index  fing-ers,  and  a  fourth,  which  after  receiving  a  communi- 
cation from  the  dorsal  cutaneous  branch  of  the  ulnar,  divides 
to  supply  the  adjacent  sides  of  the  middle  and  ring  fingers. 

The  Posterior  Interosseous. 

The  Posterior  hiterosseous  Nerve,  the  second  terminal 
branch  of  the  musculo-spiral,  commencing  while  the  latter 
nerve  lies  between  the  supinator  longus  and  brachialis  anticus, 
passes  across  the  elbow  joint  to  the  supinator  brevis  muscle, 
and  runs  directly  through  the  substance  of  that  muscle.  It 
passes    through    the   supinator    brevis    to    the    back    of    the 


438  DESCRIPTIVE  ANATOMY. 

forearm ;  and  runs  downward  on  the  posterior  face  of  the 
interosseous  membrane  to  reach  the  back  of  the  wrist,  where 
it  has  a  small  g-ang-liform  enlargement  upon  it,  and  receives  a 
communication  from  the  anterior  interosseous  branch  of  the 
median.  Its  distribution  is  to  all  of  the  muscles  on  the  back 
of  the  forearm,  with  the  exception  of  the  anconeus,  supinator 
longus,  and  extensor  carpi  radialis  long-ior.  The  muscles 
supplied  are  the  extensor  carpi  radialis  brevior,  the  supinator 
brevis,  the  extensor  communis  dig-itorum,  the  extensor  minimi 
digiti,  the  extensor  carpi  ulnaris,  the  extensor  ossis  metacarpi 
pollicis,  the  extensor  primi  internodi  pollicis,  extensor  secundi 
internodi  pollicis,  and  the  extensor  indicis. 

The  above  description  of  this  nerve,  the  usually  accepted 
one,  appears  to  be  incorrect.  It  should  be  said  that  the  musculo- 
spiral  nerve  supplies  all  the  muscles  on  the  back  of  the  arm 
and  forearm  without  using-  the  useless  term  "posterior  inter- 
osseous nerve  ;"  and  the  radial  should  be  described  as  a  way- 
side branch  of  the  nerve,  as  it  really  is.  The  above  description 
is  g-iven  in  conformity  with  custom. 

The  Circumflex  Nerve. 

The  Circumflex  Nerve  is  the  last  of  the  terminal  branches 
of  the  Brachial  plexus.  Arising-  from  the  posterior  cord,  in 
common  with  the  musculo-spiral,  it  passes  downward  on  the 
subscapularis  to  the  lower  border  of  that  muscle,  being-  a 
posterior  relation  of  the  third  portion  of  the  axillary  artery. 
It  now  passes  to  the  back  of  the  humerus,  running-  throug-h  the 
quadrilateral  interval  bounded  above  by  the  teres  minor,  below 
by  the  teres  major,  internally  by  the  long-  head  of  the  triceps 
and  externally  by  the  shaft  of  the  humerus.  It  accompanies 
the  posterior  circumflex  artery.  The  nerve  now  divides  into 
an  upper  and  a  lower  branch — the  upper  to  accompany  the 
posterior  circumflex  vessels,  winding-  around  the  surg-ical  neck 
of  the  humerus,  beneath  the  deltoid  muscle,  which  it  pierces, 
supplying-  that  muscle  and  the  skin  over  its  lower  part.  The 
lower  branch  distributes  filaments  to  the  teres  minor  and 
back  of  the  deltoid  and  pierces  the  deep  fascia  to  reach  the 
skin  covering-  the  lower  part  of  the  deltoid  and  the  long-  head 
of  the  triceps.  The  nerve  gives  an  articular  filament  to  the 
shoulder  joint. 


THE  CENTRAL  NERVOUS  SXSTEM.  439 

Dorsal  Spinal  Nerves. 

The  dorsal  spinal  nerves  are  izuelve  pairs,  the  posterior 
branches  of  which  are  distributed  to  the  structures  of  the  back, 
while  the  anterior  cords  form  the  intercostal  nerves,  and,  un- 
like other  spinal  nerves,  do  not  form  a  plexus  but  are  distrib- 
uted separately. 

The  Intercostal  Nerves. 

The  Intercostal  Nerves  are  the  anterior  cords  of  the  twelve 
dorsal  nerves,  and  derive  their  name  from  their  course  forward 
between  the  ribs. 

The  first  dorsal  nerve  sends  almost  all  its  bulk  to  the  bra- 
chial plexus,  and  the  tzcelfth  usually  gives  a  branch  to  the 
lumbar  plexus.  The  intercostal  nerves  are  intended  for  the 
supply  of  the  muscles  among-  which  they  course,  and  of  the 
integ-umenton  the  front  and  sides  of  the  thorax  and  abdomen. 
Each  intercostal  nerve  runs  forward  in  the  intercostal  space 
between  the  intercostal  muscles  to  near  the  edg-e  of  the  sternum 
where  it  turns  forward  and  becomes  superficial,  being-  called 
the  anterior  cutaneous.  It  is  then  distributed  to  the  integ-ument 
of  the  front  of  the  chest  and  abdomen,  most  of  the  filaments 
passing-  outward  in  a  recurrent  course.  The  six  upper  nerves 
appear  as  the  anterior  cutaneous  throug-h  the  corresponding- 
intercostal  spaces,  while  the  six  lower  pierce  the  sheath  of  the 
rectus  muscle,  and  are  called  the  anterior  cutaneous  of  the 
abdomen.  After  reaching-  the  extremities  of  the  intercostal 
spaces  these  last  nerves  pass  on  between  the  broad  muscles  of 
the  abdomen,  and  the  last  one,  thoug-h  called  intercostal,  is 
really  not  one  since  it  lies  below  the  last  rib.  Whilst  running- 
forward  the  intercostal  nerves  supply  the  intercostal  muscles 
and  the  broad  muscles  of  the  abdomen,  and  about  midway  in 
its  course  each  nerve  g-ives  off  a  branch  called  lateral  cutaneous y 
which  divides  into  two,  one  branch  passing-  forward  and  the 
other  backward,  both  being-  distributed  to  the  integ-ument  on 
the  side  of  the  chest  or  abdomen.  The  first  intercostal  nervCy 
owing-  to  the  fact  that  most  of  the  cords  from  which  it  is  de-' 
rived  g-o  to  the  brachial  plexus,  gives  off  no  lateral  branch, 
and,  to  compensate  for  this  delinquency,  the  lateral  cutaneous 
branch  of  the  second  nerve  is  remarkably  larg-e,  and  not  only 
fulfils  the  office  of  the  lateral   cutaneous  branches  for  itself 


440  DESCRIPIVE  ANATOMY. 

and  the  first,  but  under  the  name  of  intercosto-humeral ,  passes 
into  the  axilla,  where  it  communicates  with  the  lesser  internal 
cutaneous.  The  lateral  cutaneous  branch  of  the  twelfth  nerve 
descends  over  the  crest  of  the  ilium,  and  is  distributed  to  the 
integ-ument  of  the  gluteal  region. 

The  Lumbar  Spinal  Nerves. 
The  Lumbar  Spinal  Nerves  are  five  pairs,  the  posterior  cords 
of  which  are  distributed  to  the  structures  of  the  back,  while 
the  anterior  form  a  plexus,  called  the  Lumbar  Plexus,  the  last 
cord  of  the  lumbar  nerves,  however,  passing-  downward  to 
enter  into  the  formation  of  the  sacral  plexus. 
The  Lumbar  Plexus. 

The  manner  of  formation  of  the  Lumbar  Plexus  is  g-enerally 
as  follows:  The  tzuel/th  (for^a/  ^zeri'e 'g-ives  a  branch  which 
descends  in  the  substance  of  the  psoas  mag-nus  muscle  to  unite 
with  the  fi7'st  lumbar.  The  cord  thus  formed  g-ives  off  the 
ilio-hypog^astric  and  ilio-lumbar  nerves,  and  a  branch  which 
descends  to  unite  with  the  second  lumbar.  The  second  lum  bar, 
after  receiving-  this  branch,  g-ives  off  a  branch  of  distribution, 
the  g-enito-crural,  and  a  communicating-  branch,  which  descends 
to  unite  with  the  third  lumbar,  so  that  the  g-enito-crural  is  the 
product  of  the  first  and  second  lumbar.  The  cord  formed  by 
the  union  of  the  branch  from  the  second  and  third  lumbar 
nerves  g-ives  off  an  external  cutaneous  branch  and  a  branch 
which  unites  with  the  fourtli  lumbar,  conveying  to  that  nerve 
some  of  the  fibres  derived  from  the  second  as  well  as  the  third. 
The  union  of  these  branches  produces  the  anterior  crural, 
which,  therefore,  contains  fibres  from  the  second,  third,  and 
fourth  lumbar  nerves,  while  the  last  nerve  of  the  plexus,  the 
obturator,  is  the  product  of  the  third  and  fourth.  The  remain- 
ing- portion  of  the  fourth  unites  with  the  last  lumbar  to  form 
the  lumbo-sacral  cord,  which  passes  down  into  the  pelvic  cavity 
to  aid  in  the  formation  of  the  sacral  plexus. 

The  Lumbar  Plexus  resembles  in  the  manner  of  its  formation 
the  cervical.  It  is  situated  in  the  posterior  fibres  of  the  psoas 
mag-nus  muscle  ;  and  its  branches,  with  the  exception  of  the 
g-enito-crural,  pass  outward  beneath  the  posterior  surface  of 
that  muscle,  the  g-enito-crural  perforating-  the  muscle  and 
appearing-  upon  its  anterior  surface. 


THE  CENTRAL  NERVOUS  SYSTEM.  441 

Branches  of  the  Lumbar  Plexus. 

Ilio-Hypog-astric  Ilio-Ing-uinal 

External  Cutaneous  Genito- Crural 

Anterior  Crural  Obturator 

Muscular  Communicating- 

The  Branches  of  the  Lumbar  plexus,  named  in  the  order  in 
which  they  arise  from  above  downward  are  the  ilio-hypog"astric, 
ilio  ing-uinal,  external  cutaneous,  g-enito-crural,  anterior  crural, 
and  obturator.  Some  authorities  mention  the  accessory  obtu- 
rator, which  is  an  infrequent  branch.  In  addition  to  these  the 
plexus  also  gives  muscular  branches,  which  supply  the  psoas 
magfnusandquadratus  lumborum  muscles,  and  arise  irregularly 
from  the  plexus. 

Ilio-Hypogastric. 

The  Ilio-Hypog-astric,  the  product  of  the  first  lumbar  nerve, 
appears  at  the  outer  border  of  the  psoas  magnus,  crosses  the 
quadratus  lumborum  near  the  upper  end  of  that  muscle,  pass- 
ing- downward  and  outward  and  lying  behind  the  peritoneum, 
pierces  the  transversalis  muscle,  and  lies  for  a  short  distance 
between  that  muscle  and  the  internal  oblique  until  it  reaches 
a  point  from  two  to  two  and  one-half  inches  behind  the  anterior 
superior  spinous  process  of  the  ilium,  where  it  divides. 

The  iliac  brancli,  piercing-  successively  the  internal  and  ex- 
ternal oblique  muscles,  passes  downward  on  the  thigh  toward 
the  trochanter  major,  to  be  distributed  to  the  integument 
behind  the  lateral  cutaneous  branch  of  the  last  dorsal  nerve. 

The  hypogastric  branch  continues  the  direction  of  the  main 
trunk,  at  first  lying  between  the  internal  oblique  and  the 
transversalis,  and  then  between  the  internal  and  external 
oblique  muscles,  finally  piercing  the  aponeurosis  of  the  exter- 
nal oblique,  and  becoming  superficial,  to  be  distributed  to  the 
integument  over  the  lower  portion  of  the  abdomen. 

Ilio-Inguinal. 

The  Ilio- Inguinal  Nerve  arises  from  the  first  lumbar  in 
common  with  the  ilio-hypogastric,  and  passes  downward  and 
outward,  parallel  with  and  below  that  nerve,  across  the  quad- 
ratus lumborum  muscle.  After  crossing  the  iliacus  internus, 
it  pierces  the  transversalis  muscle  ;  and  between  that  muscle 


442  DESCRIPTIVE  ANATOMY. 

and  the  internal  oblique,  communicates  with  the  hypog-astric 
branch  of  the  ilio-hypog-astric.  It  then  becomes  more  super- 
ficial near  the  superficial  abdominal  ring-,  and  leaving-  the 
abdominal  cavity  throug-h  that  aperture,  passes  to  the  thigh, 
where  it  is  distributed  to  the  skin  covering-  the  inner,  upper 
front  aspect  of  the  thig-h,  and  to  the  scrotum  in  the  male  and 
to  the  labium  in  the  female. 

Genito- Crural. 

The  Genito- Crural  is  the  product  of  the  first  and  second 
lumbar  nerves.  It  passes  first  directly  forward  throug-h  the 
fibres  of  the  psoas  magnus  muscle,  and  descends  upon  that 
muscle  to  just  above  Poupart's  lig-ament,  where  it  divides  into 
a  g-enital  and  a  crural  branch. 

The  g-enital  branch  enters  at  the  deep  abdominal  ring-  ;  and 
following-  the  course  of  the  spermatic  cord,  is  lost  in  the  male 
in  the  cremaster  muscle,  which  it  supplies.  In  the  female  this 
branch  is  rudimentary  ;  but  follows  the  course  of  the  round 
ligament  and  is  lost  upon  that  structure.  It  crosses  the  ex- 
ternal iliac  artery  near  the  termination  of  that  vessel. 

The  crural  branch  passes  beneath  Poupart's  ligament ;  and 
runs  down  on  the  thig-h,  to  be  distributed  to  the  integ-ument  of 
its  inner  front  aspect  as  far  as  the  middle.  It  is  an  anterior 
relation  of  the  femoral  artery. 

The  External  Cutaneous. 

The  External  Cutaneous  Nerve  is  the  product  of  the  second 
and  third  Lumbar  nerve.  It  passes  downward  and  outward 
across  the  iliacus  internus  muscle  behind  the  peritoneum,  and 
reaches  the  notch  found  below  the  anterior  superior  spinous 
process  of  the  ilium.  It  here  leaves  the  abdominal  cavity,  and 
lies  beneath  the  fascia  lata  for  the  upper  inch  or  two  inches  of 
its  course.  It  then  pierces  the  fascia  lata,  and  becoming- 
superficial,  is  distributed  to  the  skin  on  the  outer  front  aspect 
of  the  thig-h,  its  distribution  lying-  in  the  interval  between  the 
iliac  branch  of  the  ilio-ing-uinal  and  the  middle  cutaneous  branch 
of  the  anterior  crural.  Fibres  from  this  nerve  descend  as  far 
as  the  knee  joint. 


THE  CENTRAL  NERVOUS  SYSTEM.  443 

The  Obturator. 

The  Ohtiirator  Nerve  arises  from  the  third  and  fourth  lumbar 
nerves  and  occasionally  receives  fibres  from  the  second  lumbar. 
It  passes  beneath  the  psoas  magnus  muscle,  runs  over  the 
brim  of  the  pelvis,  and  crossing-  along  just  beneath  the  pelvic 
brim,  where  it  lies  above  the  obturator  vessels,  reaches  the 
upper  angle  of  the  thyroid  foramen,  and  piercing  that  foramen 
it  divides  into  two  branches,  an  anterior  and  a  posterior.  The 
anterior  branch  is  distributed  to  the  hip  joint,  to  the  adductor 
longus,  adductor  brevis,  the  gracilis,  sometimes  to  the  pecti- 
neus,  and  has  a  cutaneous  branch  which  passes  to  the  skin  of 
the  inner  side  of  the  thigh.  The  posterior  branch  also  drops 
a  twng  to  the  hip  joint,  and  supplies  the  obturator  externus 
and  adductor  magnus  muscles. 

The  Anterior  Crural. 

The  Anterior  Crural  Nerve  is  the  largest  branch  of  the 
lumbar  plexus  ;  and  receives  fibres  from  the  second,  third,  and 
fourth  lumbar  nerves.  It  passes  downward  in  the  interval  be- 
tween the  psoas  magnus  and  iliacus  internus  muscles,  and  runs 
beneath  Poupart's  ligament,  where  it  lies  from  one-fourth  to 
one-half  an  inch  to  the  outer  side  of  the  femoral  artery.  After 
descending  for  a  very  short  distance,  rarely  more  than  one 
inch  and  generally  about  half-an-inch,  it  divides  into  branches, 
which  are  usually  described  as  suferficial,  or  cutq,neoiis, 
branches,  and  deep^  or  muscular  branches. 
Superficial  Branches. 
Middle  Cutaneous  Internal  Saphenous 

Internal  Cutaneous 
The  Middle  Cutaneous. 

The  Middle  Ciitaneoiis  Jjranch  passes  forward  superficial  to 
the  femoral  artery  ;  and  is  distributed  to  the  integument  which 
covers  the  front  of  the  thigh,  lying  between  the  internal  cuta- 
neous and  the  external  cutaneous,  which  is  a  direct  branch  of 
the  lumbar  plexus,  and  communicating  with  both  of  these 
nerves.  The  middle  cutaneous  generally  perforates  the  sar- 
torius  muscle,  and  in  doing  so,  gives  off  branches  which  sup- 
ply that  muscle. 

The  Internal  Cutaneous. 

The  Internal  Cuta^icoiis  is  smaller  than  the  middle.     It  passes 


444  DESCRIPTIVE  ANATOMY. 

inward  over  the  femoral  arter}^ ;  and  dividing"  into  an  anterior 
and  a  posterior  branch,  passes  to  the  inner  side  of  the  thigh. 
The  anterior  branch  communicates  with  the  middle  cutane- 
ous while  the  -posterior  branch  suns  along  the  edge  of  the 
sartorius  muscle,  pierces  the  fascia  lata,  and  is  distributed  to 
the  integ-ument  of  the  inner  side  of  the  thigh  as  low  down  as 
the  knee  joint,  communicating  in  its  course  with  the  cutaneous 
branch  of  the  obturator  nerve. 

The  Internal,  or  Long,  Saphenous. 

The  Internal,  or  Long'  Saphenous  Nerve  descends  in 
close  contact  with  the  outer  side  of  the  sheath  of  the  femoral 
vessels  until  it  reaches  Hunter's  canal,  where  it  becomes 
superficial  to  these  vessels.  In  the  upper  portion  of  its 
course  it  is  in  close  relationship  with  the  muscular  branch  to 
the  vastus  internus  muscle,  the  two  nerves  bearing"  almost 
exactl}^  the  same  relation  to  the  femoral  artery,  with  the 
saphenous  slightly  in  front.  At  Hunter's  canal  the  nerve 
sometimes  passes  across  that  fibrous  structure,  and  is 
separated  by  it  from  the  front  of  the  femoral  artery  ;  but 
usually  lies  on  the  femoral  arter}^  in  Hunter's  canal,  but  not 
in  the  femoral  sheath.  At  the  lower  extremity  of  Hunter's 
canal  the  nerve  passes  beneath  the  tendons  of  the  sartorius 
muscle  ;  and  accompanies  that  muscle  downward  to  its  inser- 
tion, where  it  pierces  the  insertion  between  the  sartorius  and 
the  gracilis  to  become  superficial  just  below"  the  knee.  It 
now  comes  into  relationship  with  the  internal  saphenous  vein  ; 
and  accompanies  that  vessel  to  pass  in  front  of  the  internal 
malleolus,  and  then  to  continue  its  course  onward  to  the  inner 
side  of  the  great  toe,  which  it  supplies. 

It  g"ives  off  throug-hout  its  course  cutaneous  branches, 
which  are  distributed  throug"hout  the  course  of  the  nerve.  At 
the  knee  joint  it  g-ives  one  large  branch,  the  -patella,  which 
pierces  the  sartorius,  and  running-  downward  and  outward, 
aids  in  the  formation  of  the  patella  plexus. 

Deep,  or  Muscular  Branches. 

The  deep,  or  muscular,  branches  are  a  nerve  to  the  iliacus 
internus,  given  off  while  the  anterior  crural  is  in  the  abdomi- 


THE  ce:stral  nervous  system.  445 

nal  cavity  ;  branches  to  the  pectineus  (usually  two  in  number, 
thoug-h  sometimes  but  one)  which  pass  beneath  the  femoral 
vessels  ;  a  separate  branch  occasionally  to  the  sartorius,  thougfh 
that  muscle  is  usually  supplied  by  the  middle  cutaneous  ;  and 
a  long-  branch,  already  mentioned,  the  nerve  to  the  vastus  in- 
ternus,  which  is  in  close  relationship  to  the  femoral  artery  and 
the  internal  saphenous  nerve,  enters  the  vastus  internus  just 
above  Hunter's  canal,  and  there  orives  branches  to  the 
vastus  externus  and  to  the  rectus,  each  of  these  entering- 
the    corresponding-  muscle  from  its  deep  surface. 

It  will  be  seen,  therefore,  that  the  anterior  crural  nerve  by 
means  of  one  of  its  superficial  branches,  the  middle  cutaneous, 
supplies  one  of  the  muscles  of  the  front  of  the  thig-h,  the 
sartorius  ;  while  the  two  vasti  and  the  rectus  are  supplied  by 
deep  branches  of  the  anterior  crural.  The  one  remaining* 
muscle  on  the  front  of  the  thig^h,  the  tensor  vag-ina^  femoris, 
is  supplied  by  a  branch  from  the  sacral  plexus  of  nerves. 

The  Lumbo-Sacral  Cord. 

The  last  branch  of  the  lumbar  plexus  is  a  communicating" 
branch,  called  the  Lumho-Sacral  Cord.  This  cord  is  the  joint 
product  of  the  fifth  lumbar  nerve  with  a  branch  from  the 
fourth  ;  and  passes  over  the  brim  of  the  pelvis  to  unite  with  the 
first  sacral  nerve,  commencing-  the  formation  of  the  sacral 
plexus. 

The  Sacral  Plexus. 

The  Sacral  Plexus  itself  is  the  product  of  the  lumbo-sacral 
cord,  with  Wio.  first,  second,  third,  ■a.nA  /ml/ oi  the /'oicrt/i  sn.craX 
nerves.  The  fibres  entering-  into  this  plexus  are  more  inti- 
mately united  than  in  any  other  nervous  plexus  of  the  body. 
It  is  triangular  in  outline,  the  base  of  the  triang-le  extending- 
to  the  anterior  sacral  foramina,  the  apex  being-  directed  down- 
ward and  outward  to  the  g-reat  sacro-sciatic  foramen. 

The  Lumho-Sacral  Cord,  passing-  behind  the  common  iliac 
artery,  unites  with  the  first  sacral  nerve,  then  at  a  short  dis- 
tance from  the  anterior  spinal  foramina  the  second  sacral 
unites  with  this  cord,  then  the  third,  and  lastly  the  upper  half 
of  the  fourth,  so  that  while  lying-  upon  the  pyriformis  muscle 
the   sacral    plexus   consists  of  but  a  single,  broad  triangular 


446  DESCRIPTIVE  ANATOMY. 

cord,    there  being'  no  such  communication,  followed  by  subdi- 
vision, as  there  is  in  the  case  of  the  brachial  plexus. 

The  plexus,  after  being-  formed  in  this  way,  extends  down- 
ward and  outward  to  the  upper  margin  of  the  g-reat  sciatic 
foramen,  lying-  upon  the  pyriformis  muscle,  having- the  internal 
iliac  artery  in  front  of  it,  some  branches  of  which  vessel  pass 
between  the  cords  entering-  into  the  formation  of  the  plexus 
and  having-  the  second  portion  of  the  rectum  (more  correctly, 
the  first  portion  of  the  rectum)  resting-  upon  the  cords  as  the}^ 
emerge  from  the  sacral  foramina.  On  the  left  side,  though 
separated  from  it  by  the  peritoneum,  the  end  of  the  sigmoid 
flexure  of  the  colon  would  also  rest  upon  the  front  of  this 
plexus. 

Branches  of  the  Sacral  Plexus. 

Way-side  Terminal 

Muscular         Visceral         Gluteal  Internal  Pudic 

Lesser  Sciatic  Great  Sciatic 
Besides  its  terminal  branches,  this  plexus  also  gives  off 
certain  zvayside,  or  collateral  branches,  which  are  distributed 
to  the  muscles  and  viscera  in  the  pelvic  cavity.  The  muscular 
branches  come  in  part  from  the  plexus  and  in  part  from  the 
cords  before  they  unite  to  form  the  plexus.  They  supply  the 
pyriformis,  obturator  internus,  the  gemelli  and  the  quadratus 
femoris. 

The  Terminal  Branches  are  the  Gluteal,  Internal  Pudic, 
Lesser   Sciatic,  and  Great  Sciatic  Nerves. 

The  Gluteal. 

The  Gluteal  or  Superior  Gluteal  Nerve,  as  it  is  frequently 
called,  arises  from  the  upper  portion  of  the  sacral  plexus,  and 
leaves  the  pelvic  cavity  by  passing  above  the  pyriformis  muscle 
through  the  greater  sacro-sciatic  foramen.  It  then  appears  in 
the  interval  between  the  gluteus  medius  and  the  gluteus 
minimus  muscles,  where  it  divides  into  two  branches,  superior 
and  inferior.  The  su-perior  follows  the  origin  of  the  gluteus 
minimus,  and  is  supplied  to  the  gluteus  medius  from  the  under 
surface  of  that  muscle,  while  the  inferior  passes  downward, 
forward,  and  outward,  distributing  fibres  to  the  gluteus  min- 


THE  CENTRAL  NERVOUS  SYSTEM.  447 

mus,  its  terminal  branch  ending-  in  the  tensor  vaginas  femoris. 
Inferior  Gluteal.  The  lumbo-sacral  cord  and  the  first  and 
second  sacral  nerves  g"ive  oriofin  to  the  second  sacral  nerve, 
which  frequently  arising  in  common  with  the  one  above  men- 
tioned, is  sometimes  distinguished  as  the  inferior  g-luteal.  It 
also  passes  above  the  pyriformis  muscle  through  the  greater 
sacro-sciatic  foramen,  and  enters  the  deep  face  of  the  gluteus 
minimus  muscle,  being-  distributed  to  it  by  a  number  of  small 
branches. 

The  Internal  Pudic. 

The  Internal  Pudic  Nerve  arises  from  the  lower  part  of  the 
sacral  plexus,  leaves  the  pelvic  cavity  throug-h  the  g-reater 
sacro-sciatic  foramen,  below  the  pyriformis,  crosses  the  spine 
of  the  ischium,  and  re-enters  the  pelvic  cavity  through  the 
lesser  sciatic  foramen.  It  then  courses  along-  the  internal  face 
of  the  ischium  about  an  inch  above  its  tuberosity,  passes  to  the 
ramus  of  the  ischium,  and  is  enclosed  in  the  fibrous  sheath 
called  Alcock's  canal.  It  then  passes  between  the  two  layers 
of  the  perineal  fascia,  and  terminates  by  dividing  into  two 
branches,  an  upper  one,  the  nerve  to  the  dorsum  of  the  penis, 
and  an  inferior  branch,  called  the  Perineal. 

Prior  to  this  division  the  internal  pudic  nerve  g-ives  off  an 
Inferior  Hemorrhoidal  Branch,  corresponding-  to  the  artery 
of  the  same  name,  which  is  distributed  to  the  sphincter  ani 
muscle  and  to  the  integ-ument  around  the  anus. 

Terminal  Branches  of  The  Internal  Pudic. 

Dorsalis  Penis  Perineal 

The  Dorsalis  Penis. 
The  Dorsalis  Penis  Nerve,  the  branch  to  the  back  of  the 
penis,  passes  upward  and  forward  along-  the  ramus  of  the 
ischium  and  pubes,  accompanying  the  artery  of  the  same  name, 
pierces  the  suspensory  lig-amentof  the  penis,  and  runs  forward 
upon  that  org-an  to  be  distributed  to  the  integument  that  cov- 
ers it  and  to  the  corpus  cavernosum,  while  its  terminal  branches 
end  in  the  g-lans  psnis.  In  its  course  along-  the  back  of  the 
penis  it  g-ives  off  lateral  cutaneous  branches,  which  are  distri- 
buted to  the  skin  upon  the  sides  of  the  org-an. 


448  DESCRIPTIVE  ANATOMY. 

The  Perineal. 

The  Perineal  Nerve,  the  second  branch  of  the  internal  pudic» 
divides  into  two  sets  of  bra.nches,  superficial  and  deep,  or  cu- 
taneous and  muscular. 

The  cutaneous  branches  are  two,  anterior  and  posterior, 
and  pass  upward  and  forward,  to  be  distributed  to  the  scro- 
tum, perineum,  and  under  surface  of  the  penis,  in  which  latter 
situation  they  communicate  with  the  dorsal  nerve  of  the  penis. 
In  the  female  of  course  the  upper  of  these  two  branches  would 
be  distributed  to  the  labia  majora,  the  analog-ue  of  the  scrotum 
in  the  male. 

The  muscular  branches  are  distributed  to  the  muscles  of 
the  perineum  ;  that  is,  the  transversus  perinei,  erector  penis,  ^ 
accelerator  urinae  and  compressor  urethrae,  these  names  being" 
g-iven  to  the  muscles  in  the  m.ale  subject,  each  having-  its  ana- 
log"ue  in  the  female.  That  branch  which  passes  to  the  trans- 
versus perinei  corresponds  to  the  transverse  perineal  artery. 
Some  deeper  branches  of  this  nerve  also  enter  the  corpus, 
spongiosum,  and  supply  that  body,  with  its  attached  muscles. 

The  Lesser  Sciatic. 

The  Lesser  Sciatic  Nerve  usually  arises  by  two  roots.  It 
passes  from  the  pelvic  cavity  throug-h  the  g-reater  sacro-sciatic 
foramen  below  the  pyriformis  muscle,  and  runs  down  opposite 
the  middle  of  the  interval  between  the  trochanter  major  and  the 
tuberosity  of  the  ischium,  lying-  beneath  the  g-luteus  maximus 
muscle.  It  emerg-es  from  the  lower  border  of  this  muscle  : 
and  pursuing"  its  course  down  the  back  of  the  thig-h,  beneath 
the  fascia  lata  reaches  the  superior  ang-le  of  the  popliteal  space, 
where  it  breaks  up  into  its  terminal  branches,  which  after 
being-  distributed  to  the  skin  covering-  the  popliteal  space, 
anastomose  with  the  cutaneous  branch  from  the  g-reat  sciatic 
and  with  the  plexus  around  the  patella. 

This  nerve  is  almost  entirely  a  cutaneous  branch,  except  for 
the  set  of  fibres  which  enters  the  g-luteus  maximus  muscle, 
that  muscle  receiving-  its  nerve  supply  entirely  from  the  sacral 
plexus,  thoug-h  some  of  the  fibres  pass  to  it  from  the  inferior 


THE  CENTRAL  NERVOUS  SYSTEM.  449 

g-luteal  while  the  remaining-  branches  come  from  the  lesser 
sciatic.  The  latter  branches  emerg-e  from  below  the  lower 
border  of  the  muscle,  and  then  reverse  their  course  to  enter  it 
from  its  deep  surface. 

The  cutaneous  branches  are  distributed  to  the  skin  on  the 
back  of  the  thig-h  as  far  down  as  the  popliteal  space.  One 
branch  of  larg^e  size  is  individualized  as  a  separate  nerve, 
called  the  Inferior  Pudendal. 

The  Inferior  Pudendal  curves  forward,  running-  below  the 
tuber  ischii,  passes  to  the  scrotum  in  the  male  and  the  labia  in 
the  female,  communicating-  with  the  superficial  perineal  and 
the  terminal  branch  of  the  inferior  hemorrhoidal. 

The  Great  Sciatic. 

The  Great  Sciatic  is  the  long-est  and~  larg-est  nerve  in  the 
body.  It  appears  to  be,  and  in  reality  is,  a  continuation  of  the 
sacral  plexus.  Triang-ular  at  its  commencement,  it  soon  becomes 
circular  in  form.  It  emerg-es  from  the  pelvic  cavity  below  the 
pyriformis  muscle  throug-h  the  g-reater  sacro- sciatic  foramen, 
being-  the  last  of  the  numerous  structures  which  emerg-e 
from  this  foramen.  These  structures  are  seven  in  number. 
Two  of  them  pass  above  the  pyriformis,  and  the  remaining- 
five  below  that  muscle.  Those  which  pass  above  the  pyri- 
formis are  the  g-luteal  nerve  and  artery;  those  passing-  below  it 
are  the  internal  pudic,  the  lesser  sciatic  and  g-reat  sciatic  nerves, 
the  internal  pudic  and  ischiatic,  or  sciatic,  arteries.  This  does 
not  complete  the  total  number  of  structures  which  pass 
throug-h  this  foramen,  because  in  addition  should  be  mentioned 
the  pyriformis  muscle  itself  and  the  companion  veins  of  the 
arteries  named. 

After  escaping-  from  the  pelvis,  the  g-reat  sciatic  nerve 
passesdown  the  middle  of  the  back  of  the  thig-h,  resting-  on  the 
adductor  mag-nus  muscle,  and  covered  by  the  muscles  which 
arise  from  the  tuberosity  of  the  ischium.  Two  of  these  mus- 
cles, the  semi-tendinosus  and  semi-membranosus,  quickly  pass 
to  its  inner  side,  while  the  biceps  covers  the  nerve  for  some 
distance  down  the  thig-h.  At  the  upper  ang-le  of  the  popliteal 
space  (formed   externally  by  the  biceps  and    internally  by  the 

Des  Anat— 29 


450  DESCRIPTIVE  ANATOMY. 

semi-tendiuosus  and  semi-membranosus  muscles)  the  nerve 
appears  between  these  muscles,  called  the  "ham-string*"  mus- 
cles. It  then  passes  into  the>  popliteal  space,  and  divides  into 
its  two  terminal  branches,  the  Internal  and  External  Popliteal 
Nerve. 

The  point  of  division  is  variable,  and  may  exist  anywhere 
between  the  sacral  plexus  and  the  centre  of  the  popliteal  space. 
In  a  few  rare  cases  the  internal  and  external  popliteal  nerves 
come  off  separately  from  the  sacral  plexus;  and  in  such  cases 
they  are  sometimes  separated  from  one  another  by  the  fibres 
of  the  pyriformis  muscle.  In  other  cases  the  division  takes 
place  below  the  tuberosity  of  the  ischium,  and  in  still  other 
cases  at  the  middle  of  the  popliteal  space.  As  the  nerves  are 
bound  tog-'ether  simply  by  connective  tissue,  the  dissector  may 
split  them  up  to  any  point  between  the  popliteal  space  and  the 
orig"in  of  the  two  nerves  from  the  sacral  plexus. 

The  point  of  termination  usually  g^iven  for  the  g"reat  sciatic 
is  the  superior  angfle  of  the  popliteal  space  ;  but  it  rarely  di- 
vides before  reaching-  a  lower  point,  so  that  the  gfreat  sciatic 
itself,  instead  of  its  internal  popliteal  branch,  becomes  a  rela- 
tion of  the  popliteal  artery. 

Before  dividing-  into  terminal  branches,  the  great  sciatic 
g-ives  off  muscular  branches  to  supply  the  posterior  femoral 
group,  cutaneous  branches  which  communicate  with  the  lesser 
sciatic  nerve,  and  a  branch  to  the  adductor  magfnus. 

Branches  of  the  Great  Sciatic. 

Internal  Popliteal  Ij^xternal  Popliteal 

The  Internal  Popliteal. 

The  Internal  Popliteal  Nerve,  the  larg-erof  the  two  terminal 
branches  of  the  g-reat  sciatic,  commences  below  the  upper 
angle  of  the  popliteal  space,  to  pass  throug-h  that  space,  and 
terminate  by  becoming-theposterior  tibial  nerve.  As  it  enters 
at  the  apex  of  the  popliteal  space,  it  necessarily  lies  to  the 
outer  side  of,  and  superficial  to,  the  popliteal  artery  and  vein; 
but  the  nerve  has  an  inclination  inward,  while  the  inclination 
of  the  artery  is  outward,   hence  at  the  middle  of   the  popliteal 


THE  CENTRAL  NERVOUS  SYSTEM.  451 

Space,  opposite  the  posterior  lig-ament  of  the  knee  joint,  the 
nerve  is  found  directly  behind  the  artery,  with  the  vein  inter- 
posed between  itself  and  the  artery,  while  at  the  termination 
of  the  popliteal  space  both  nerve  and  vein  have  become  inter- 
nal to  the  artery,  the  vein  still  lying-  between  the  nerve  and  the 
artery.  At  the  lower  border  of  the  popliteus  muscle,  at  a 
point  which  corresponds  to  the  junction  of  the  upper  one-fifth 
with  the  lower  four-fifths  of  the  shaft  of  the  tibia,  the  internal 
popliteal  nerve  terminates  by  changfino-  its  name  to  the  Poste- 
rior Tibial. 

The  nerve,  like  the  other  important  structures  contained 
in  this  diamond-shaped  space,  has  the  internal  ham-string- 
muscles  to  its  inner  side  above,  and  the  inner  head  of  the  gas- 
trocnemius below,  while  to  its  outer  side  are,  above,  the  biceps, 
and  below,  the  outer  head  of  the  g-astrocnemius  and  the  plan- 
taris  muscles.  It  is  covered  by  the  strong-  fascia  which  extends 
between  these  muscles  and  roofs  in  the  entire  space. 

Branches  of  the  Internal  Popliteal. 

Articular  Muscular,  or  Sural  Cutaneous 

The  Branches  of  the  Internal  Popliteal  are  divided  into 
three  sets,  articular,  muscular,  and  cutaneous. 

The  Articular  Branches  are  three  in  number  ;  and  are 
known  as  Superior  and  Inferior  Internal  Articular,  and 
Azygos  Articular.  They  accompany  the  arteries  of  the  same 
name  ;  and  are  distributed  in  the  same  way.  They  anastomose 
with  one  another,  and  with  the  other  nerves  which  surround 
the  knee  joint,  passing-  as  far  as  the  patella  plexus,  while  the 
azygos  articular,  piercing,  with  the  corresponding-  artery, 
the  posterior  ligament  of  the  knee,  is  distributed  to  the  s^^no- 
vial  membrane  in  the  interior  of  that  joint. 

The  Muscular,  or  Sural  (L.  Sura,  the  calf  of  the  leg). 
Branches  accompanying  the  sural  branches  of  the  popliteal 
artery,  are  distributed  to  the  two  heads  of  the  gastrocnemius 
and  to  the  plantaris  muscle. 

In  addition  to  these  sural  branches,  the  internal  popliteal 
nerve  gives  off  the  branches  which  supply  the  popliteus  muscle. 
These   branches,  two  in  number,  pass  down  to  the  lower  bor- 


452  DESCRIPTIVE  ANATOMY. 

der  of  the  popliteus  muscle,  and,  reversing-  their  course,  pass 
upward  between  that  muscle  and  the  posterior  surface  of  the 
interosseous  membrane,  to  enter  the  muscle  from  its  deep  face. 
The  only  Cutaneous  Branchy  the  External  Saphenous,  or 
Communica7is  Poplitei,  passes  downward  in  the  interval  be- 
tw^een  the  two  heads  of  the  g-astrocnemius  muscle,  lies  in  the 
g-roove  upon  the  posterior  surface  of  the  belly  of  that  muscle, 
accompanied  by  the  external  saphenous  vein  ;  and,  about  the 
middle  of  the  calf  of  the  leg-,  receives  a  branch  of  communica- 
tion from  the  external  popliteal  nerve,  this  branch  being-  called 
the  Conimunicayis  Peronei.  After  receiving-  this  branch  it 
continues  downward,  with  a  slig-ht  inclination  out^yard,  passes 
behind  the  external  malleolus,  and  reaching-  the  dorsum  of  the 
foot,  is  distributed  to  the  integ-ument  on  the  back  of  the  leg-, 
the  outer,  back  part  of  the  ankle,  and  the  outer  side  of  the 
foot  as  far  as  the  little  toe,  where  it  commumicates  with  a 
branch  of  the  musculo-cutaneous  nerve. 

The  Posterior  Tibial. 

The  Posterior  Tibial  Nerve  is  a  continuation  of  the  internal 
popliteal ;  and  commences  where  that  nerve  terminates  at  the 
lower  border  of  the  popliteus  muscle.  It  at  first  lies  to  the 
inner  side  of  the  posterior  tibial  artery  ;  but  about  two  inches 
below  the  orig-in  of  that  vessel,  crosses  it  superficially  opposite 
the  orig-in  of  the  peroneal  branch,  and  lies  for  a  short  distance 
in  the  interval  between  the  peroneal  and  posterior  tibial  arte- 
ries. It  then  descends  to  the  outer  side  of  the  posterior  tibial, 
and  remains  a  continuous  external  relation  of  that  vessel  to  its 
termination,  but  lies  on  a  plane  posterior  to  it. 

It  divides  midway  between  the  inner  malleolus  and  the  pos- 
terior tuberosity  of  the  os  calcis  into  the  internal  and  exter- 
nal plantar  branches. 

Branches— Way-Side. 

The  Branches  of  the  Posterior  Tibial  Nerve  are  muscular 
branches,  which  supply  the  tibialis  posticus,  flexor  long-us  pol- 
licis,  and  the  flexor  long-us  dig-itorum.  At  the  ankle  joint, 
however,  itg-ives  off  calcanean  branches,  which,  accompanying- 


THE  CENTRAL  NERVOUS  SYSTEM.  453 

the  corresponding-  arteries,  are  distributed  to  the  skin  on  the 

inner  aspect  of  the  heel,  and  an  articular  branch  which  supplies 

the  ankle  joint. 

Terminal  or  Plantar. 

Internal  Plantar  External  Plantar 

The  Internal  and  External  Plantar  Nerves  differ  from  one 
another,  and  more  distinctly  from  the  internal  and  external 
plantar  arteries,  because  while  the  internal  plantar  artery  is 
smaller  in  size  than  the  external,  aud  has  a  less  extended  dis- 
tribution, the  internal  plantar  nerve  is  largfer  than  the  exter- 
nal. The  internal  plantar  nerve  corresponds  in  in  its  distri- 
bution to  the  median  nerve  of  the  hand  ;  while  the  external 
plantar  corresponds  to  the  ulnar  nerve  in  the  hand.  That  is, 
the  internal  plantar  nerve  supplies  three  toes  and  a  half,  equal 
to  the  three  and  one  half  fing-ers  of  the  median  ;  while  the  ex- 
ternal plantar  supplies  one  toe  and  a  half,  the  equivalent  of 
the  ulnar  of  the  hand. 

The  Internal  Plantar. 

The  Internal  Plantar  Nerve  passes  forward  as  the  companion 
of  the  internal  plantar  artery,  supplies  the  inner  half  of  the 
flexor  brevis  dig-itorura,  then  continuing-  its  course  it  g-ives  a 
branch  to  the  abductor  pollicis  and  to  the  two  internal  lumbrical 
muscles,  and  to  the  flexor  brevis  pollicis  and  articular  branches 
to  the  tarsus  and  metatarsus. 

It  then  divides  into  its  terminal  branches,  the  most  internal 
of  which  passes  to  the  inner  side  of  the  g-reat  toe,  the  second 
to  the  cleft  between  the  second  and  g-reat  toes,  where  it  divides 
into  branches  for  the  inner  side  of  these  two  toes,  the  third  to 
the  cleft  between  the  second  and  third,  and  the  fourth,  after 
giving-  off  a  brauch  of  communication  to  the  external  plantar, 
runs  to  the  cleft  between  the  third  and  fourth  toes  and  supplies 
the  adjacent  sides  of  these  toes. 

The  External  Plantar. 

The  Exter7ial Plantar  Nerve  ^ccom\idimQ^  the  external  plan- 
tar artery,  passes  beneath  the  orig-in  of  the  flexor  brevis 
digitorum,  and   lies    between  that  muscle  and   the  Abductor 


454  DESCRIPTIVE  ANATOMY. 

minimi  digiti.  It  then  runs  forward  as  far  as  the  posterior 
extremity  of  the  fifth  metatarsal  bone.  It  then  plunges  be- 
neath the  second  layer  of  muscles  on  the  sole  of  the  foot,  and 
accompanies  the  arch  formed  by  the  external  plantar  artery. 
In  this  course  it  supplies  the  abductor  minimi  dig-iti,  the  outer 
half  of  the  flexor  brevis  minimi  dig-iti,  the  second  layer  of 
muscles  on  the  foot,  then  the  flexor  accessorious,  and  the  two 
outer  lumbricals,  and  g-ives  branches  to  the  interosseous  mus- 
cles occupying- the  third  and  fourth  interosseous  spaces.  As  it 
passes  between  the  second  and  third  layers  of  the  foot  it  supplies 
all  the  muscles  of  the  third  layer  of  the  sole.  Its  digital 
branches  are,  one  to  the  outer  side  of  the  little  toe,  and  one, 
which  after  communicating-  with  the  internal  plantar,  divides 
at  the  cleft  between  the  fourth  and  fifth  toes  and  supplies  the 
adjacent  sides  of  these  toes. 

The  External  Popliteal. 

The  External  Popliteal  nerve  beg-ins  as  a  branch  of  the 
great  sciatic,  near  the  upper  ang-le  of  the  popliteal  space,  passes 
downward  and  outward  and  is  only  momentarily  a  relation 
of  the  popliteal  artery,  lying-  superficial  to  it  and  to  its  outer 
side.  It  then  passes  behind  the  external  tuberosity  of  the  femur, 
crosses  the  head  of  the  fibula,  and  plung-ing-  into  the  substance 
of  the  peroneus  long-us  muscle,  terminates  there  by  dividing- 
into  the  anterior  tibial  and  the  musculo-cutaneous  nerves. 
The  relation  of  this  nerve  to  the  popliteal  artery  is,  as  before 
mentioned,  only  momentary,  except  in  those  cases  in  which 
the  nerve  is  so  closely  bound  to  the  internal  popliteal  as  to  di- 
verg-e  from  that  nerve  at  the  middle  of  the  popliteal  space. 

Branches. 

Way-    j  Articular  Termi-  j  Anterior  Tibial 

Side  \  Communicans  Peronei         nal       (  Musculo-Cutaneous 

In  all  cases  the  external  popliteal  nerve  gives  oJ0P  tzvo  articu- 
lar branches  corresponding-  to  the  superior  external  and  infe- 
rior external  articular  arteries,  these  branches  accompanying* 
the  arteries  and  being-  distributed  in  the  same  way.  A  recur- 
rent articular  branch  is  also  g-iven  off  which  accompanies  the 
anterior  tibial  artery  and  supplies  the  front  of  the  knee. 


THE  CENTRAL  NERVOUS  SYSTEM.  455 


The  Communicans  Peronei. 

Below  the  knee  joint  the  external  popliteal  g-ives  off  the 
Communicans  Peronei,  which  unites  with  the  communicans 
poplitei  to  form  the  External  Saphenous  Nerve  and  to  be 
distributed  with  that  nerve. 

The  Anterior  Tibial. 

Of  the  two  terminal  branches  of  the  external  popliteal  the 
Anterior  Tibial,  after  passing-  throug-h  the  fibres  of  the  pero- 
neus  long-US,  lies  between  that  muscle  and  the  extensor  longus 
dig-itorum.  It  then  passes  to  the  front  of  the  interosseous 
membrane,  having-  passed  obliquely  beneath  the  extensor  lon- 
g-us  dig-itorum,  and  becomes  a  relation  of  the  anterior  tibial 
artery,  having-  the  same  muscular  relations  with  that  vessel ; 
viz.,  for  the  upper  third  to  its  outer  side  is  the  extensor  long-us 
dig-itorum,  to  its  inner  side  the  tibialis  anticus  :  in  the  middle 
third  the  extensor  proprius  pollicis  to  the  outer  side  and  the 
tibialis  anticus  still  to  the  inner  side.  In  the  lower  third  it 
has  the  extensor  long-us  dig-itorum  to  the  outer  side  and  the 
extensor  proprius  pollicis  to  the  inner  side,  which  muscle  has 
crossed  to  the  front  of  the  nerve  and  displaced  the  tibialis 
anticus.  To  the  artery  it  bears  a  triple  relation,  lying-  first 
to  the  outer  side  and  resting-  on  the  interosseous  membrane, 
then  for  the  middle  third  of  the  anterior  tibial  artery  the  nerve 
rests  on  its  front,  separated  by  the  artery  from  the  interosse- 
ous membrane,  and  in  the  lower  third  of  the  vessel  the  nerve 
drops  to  the  outer  side,  and  maintains  that  relation  to  the  front 
of  the  ankle  joint. 

At  the  front  of  the  ankle  joint  the  nerve  passes  beneath  the 
anterior  annular  lig-ament,  but  does  not  chang-e  its  name  as  the 
artery  does.  To  the  dorsalis  pedis  artery  it  maintains  the  same 
relation  which  it  bore  to  the  anterior  tibial,  lying-  on  the  outer 
side  of  that  vessel.  It  continues  as  far  as  the  cleft  between  the 
g-reat  and  second  toes,  where  it  divides  into  two  branches  to 
supply  the  adjacent  sides  of  these  two  toes,  after  having-  com- 
municated  with  the  long-   saphenous    branch  of  the   anterior 


456  DESCRIPTIVE  ANATOMY. 

crural  nerve  on  the  inner  side  of  the  great  toe,  its  outer  branch 
communicating  with  the  musculo-cutaneous. 

Branches. 

The  Anterior  Tibial  Nerve  in  its  course  over  the  leg  supplies 
branches  to  the  tibialis  anticus,  extensor  long-us  digitorum,  and 
extensor  proprius  poUicis,  while  on  the  outer  side  it  has  a 
gangliform  enlargement  which  corresponds  to  that  on  the 
posterior  interosseous  of  the  forearm  from  which  are  given  off 
branches  to  supply  the  flexor  brevis  digitorum  muscle  and  the 
tarsal  and  metatarsal  articulations. 

The  Musculo-Cutaneous. 

The  Musculo-Cutaneous  Nerve,  after  being  formed  bv  the 
division  of  the  external  popliteal,  passes  downward,  first  in 
the  fibres  of  the  peroneus  longus  muscle,  then  in  the  interval 
between  that  muscle  and  the  peroneus  brevis,  then  between 
the  tvi/^o  perouei  muscles  and  the  extensor  longus  digitorum. 
Running  across  on  the  front  of  the  external  malleolus,  it  passes 
on  to  the  dorsum  of  the  foot,  where  it  breaks  up  into  cutane- 
ous branches  to  supply  the  toes  between  the  outer  face  of  the 
second  toe  and  the  inner  face  of  the  little  toe,  and  gives  a  twig 
to  the  inner  side  of  the  great  toe. 

In  its  course  through  the  leg  it  gives  off  branches  which 
supply  the  peroneal  muscles.  As  it  passes  across  the  external 
malleolus  it  gives  a  branch  w^hich  corresponds  to  the  external 
calcanean  branches  of  the  anterior  tibial  artery;  and  these 
branches  are  distributed  to  the  skin  on  the  outer  aspect  of  the 
heel. 

The  distribution  of  the  nerve  on  the  dorsum  of  the  foot  is 
very  irregular.  The  most  frequent  arrangement  is  that  it 
communicates  on  the  outer  side  of  the  little  toe  with  the  exter- 
nal saphenous  nerve,  then  gives  a  branch  which  passes  to  the 
cleft  between  the  little  and  the  fourth  toes  and  supplies  them, 
a  third  branch  to  the  cleft  between  the  fourth  and  third  toes, 
and  a  fourth  branch  to  the  cleft  between  the  third  and  second 
toes — which   branch    communicates    with    the   anterior    tibial 


THE  CENTRAL  NERVOUS  SYSTEM.  457 

nerve, — and  a  branch  to  the  inner  side   of  the  great  toe  which 
communicates  with  the  long  saphenous. 

It  will  be  seen  that  the  distribution  of  the  nerves  on  both 
the  back  of  the  hand  and  the  back  of  the  foot  is  quite  as  irreg- 
ular as  the  distribution  of  the  arteries  in  the  same  situation. 
In  some  instances  the  anterior  tibial  nerve  has  been  seen  to 
suppl}'  the  great,  the  second,  and  half  of  the  third  toe;  and, 
in  other  cases,  the  musculo-cutaneous  supplies  the  little,  fourth, 
third,  and  second  toes;  while  in  but  few  cases  have  I  been  able 
to  trace  the  internal  saphenous  to  the  extremity  of  the  great 
oe,  or  the  external  saphenous  to  the  extremity  of  the  little  toe. 


458  DESCRIPTIVE  ANATOMY. 


THE  CHANIAL  NERVES. 

The  crauial  nerves  comprise  twelve  pairs,  one  on  each  side, 
those  of  one  side  having"  their  counterpart  on  the  other. 

The  definition  of  a  cranial  nerve  is  that  it  appears  at  the 
base  of  the  brain  and  emerges  throug-h  an  aperture  in  the 
skull.  The  point  on  the  base  of  the  brain  where  the  nerve 
appears  is  called  its  apparent  origin,  since  it  may  be  traced 
into  the  interior  of  the  brain  to  what  is  called  its  real,  or  deep, 
origin.  The  real  origin  of  many  of  the  nerves  is  still  a 
matter  of  dispute. 

The  cranial  nerves  are  named  numerically,  in  pairs,  from 
before  backward  ;  besides  which  each  pair  is  known  by  another 
or,  in  some  cases,  several  other  names  derived  from  the  part 
to  which  the  nerve  is  distributed.  The  following  table  gives 
the  synonyms  of  the  twelve  pairs  : 

•First  Pair,  Olfactory. 
Second  Pair,  Optic. 
Third  Pair,  Motores  Oculorum. 
Fourth  Pair,  Pathetic  (Trochleares). 
Fifth  Pair,  Trifacial  (Trigeminus). 
Sixth  Pair,  Abducentes. 
Seventh  Pair,  Facial  (Portio  Dura). 
E^ighth  Pair,  Auditory,  (Portio  Mollis). 
Ninth  Pair,  Glosso- Pharyngeal. 
Tenth  Pair,  Pneumogastric,  Par  Vagum,  Vagus. 
Eleventh  Pair,  Spinal  Accessory. 
Twelfth  Pair,  Hypoglossal. 

These  twelve  pairs  were  formerly  considered  as  only  nine 
from  the  fact  that,  as  will  be  seen,  thej^  emerge  through  nine 
foramina  of  the  cranium  at  the  base.  The  classification  into 
nine  pairs  is  known  as  that  of  Willis  and  the  one  just  given  as 
that  of  Sommerring.  The  two  classifications  are  similar  for 
the  first  six  pairs,  the  seventh  pair,  in  Willis'  classification, 


THE  CRANIAL  NERVES.  459 

consisted  of  the  seventh  and  eighth,  while  the  eig-hth  consisted 
of  the  glosso-pharyng-eal,  pneumog*astric  and  spinal  accessory, 
and  the  ninth  of  the  hypoglossal, 

A  general  outline  of  the  cranial  nerves  successively,  from 
their  apparent  origin  to  their  point  of  emergence,  will  first  be 
given  and  afterwards  each  pair  will  be  taken  up  and  described. 

The  first  seen  on  the  base  of  the  brain  from  before  back- 
ward is  WiQ  first  pair.  The  first  nerve  lies  on  the  under  sur- 
face of  the  anterior  lobe  of  the  cerebrum  in  a  groove  a  little 
external  to  the  longitudinal  fissure,  having  its  commencement 
by  a  three  forked  origin  just,  in  front  of  the  anterior  perfo- 
rated space.  Near  the  anterior  extremity  of  the  anterior  cere- 
bral lobe  it  enlarges  into  an  oval-shaped  mass  which  lies  upon 
the  cribriform  plate  of  the  ethmoid  bone  and  sends  its  branches 
of  distribution  through  the  foramina  seen  there. 

The  second  nerve  is  first  seen  under  the  name  of  the  optic 
tract,  approaching  its  fellow  from  the  outer  aspect  of  the 
crus  cerebri  and  passing  beside  the  tuber  cinereum  and  uniting 
in  front  of  it  with  its  fellow  to  form  the  optic  chiasm  or  com- 
missure from  which  the  two  optic  nerves  diverge  forward  to 
enter  the  orbit  through  the  optic  foramina. 

The  third  nerve  is  seen  emerging  to  the  inner  side  of  the 
crus  cerebri,  just  in  front  of  the  pons  Varolii,  and  runs 
forward  to  leave  the  cranium  through  the  anterior  lacerated 
foramen. 

Th.Q/ourth  nerve  has  its  apparent  orign  external  to  the  third, 
on  the  optic  side  of  the  crus  cerebri,  and  also  has  its  exit 
through  the  anterior  lacerated  foramen. 

Th.Q  fifth  is  the  largest  of  the  cranial  nerves  and  is  first  seen 
just  behind  the  origin  of  the  fourth.  It  pierces  the  lateral 
aspect  of  the  pons  Varolii  and  splits  into  three  portions, 
opthalmic,  superior  and  inferior  maxillary,  which  require  three 
apertures  of  exit  from  the  cranium. 

The  opthalmic  leaves  through  the  anterior  lacerated  fora- 
men, the  superior  maxillary  through  the  foramen  rotundum, 
the  inferior  maxillary  through  the  foramen  ovale. 

The  sixth  nerve  takes  its  apparent  origin  behind  that  of  the 
fifth  from  the  upper  constricted  portion  of  the  medulla  oblon- 


460  DESCRIPTIVE  ANATOMY. 

gata,  just  behind  the  pons  Varolii,  and  passes  forward  to 
gain  eg'ress  throug-h  the  anterior  lacerated  foramen,  which  is 
thus  seen  to  transmit  three  entire  cranial  nerves,  viz  :  third, 
fourth  and  sixth,  and  a  part  of  another,  viz:  the  opthalmic 
branch  of  the  fifth. 

The  seventh^  eig'hth,  ninth,  tenth  and  eleventh  all  arise  in 
the  order  named,  from  above  downward,  in  the  g'roove  between 
the  corpora  olivare  and  restiformia  of  the  medulla  oblong-ata. 
The  seventh  and  eig'hth  leave  the  cranium  through  the  same 
opening-,  the  internal  auditory  meatus,  while  the  ninth,  tenth 
and  eleventh  all  g-ain  exit  through  the  posterior  lacerated  for- 
amen. 

The  tzvelfth  has  its  apparent  orig-in  to  the  inner  side  of  the 
five  preceding-  nerves,  from  the  groove  between  the  corpora 
olivare  and  pyramidale,  by  numerous  filaments  which  are 
speedily  collected  into  two  cords,  which  unite  to  form  the 
nerve  as  it  emerg-es  through  the  anterior  condyloid  foramen. 

The  First  Nerve. 

The  first  or  olfactory  nerve  arises  by  three  forks  or  roots, 
close  to  the  anterior  perforated  space.  The  external  or  long* 
root  consistsof  white  fibres  and  may  be  traced  along  the  fissure 
of  Sylvius  into  the  middle  lobe  of  the  cerebrum;  the  middle 
root  is  of  g"ray  matter  and  springs  from  the  posterior  part  of 
the  anterior  lobe  ;  the  inner  or  short  root  is  of  white  fibres 
and  also  arises  from  the  posterior  part  of  the  anterior 
lobe.  The  three  roots  unite  to  form  the  nerve,  just  in 
front  of  the  anterior  perforated  space,  which  passes  forward, 
triangular  in  shape  and  grayish  in  color,  lying-  in  a  groove  on 
the  under  surface  of  the  anterior  lobe  of  the  cerebrum  a  little 
external  to  the  longitudinal  fissure.  The  nerve  swells  into  an 
oblong-  g-rayish  enlargement,  called  the  hnlbiis  olfactorius, 
which  lies  beside  the  crista  g-alli  on  the  cribriform  plate  of  the 
ethmoid  bone.  From  the  under  surface  of  the  olfactory  bulb 
are  g-iven  off  some  twenty  filaments,  which  descend  into  the 
nose  throug-h  the  foramina  of  the  cribriform  plate  to  be  distri- 
buted to  the  mucous  membrane  of  the  nose  as  far  down  as  the 
middle  turbinated    bone.     These   filaments    are  arrang-ed  in 


THE  CRANIAIv  NERVES  461 

three  sets,  viz:  those  to  the  septum,  those  to  the  external  wall 
and  those  to  the  roof  of  the  nose. 

Second  Nerve. 

The  second  ov  optic  nerve  has  its  apparent  orig-in  just  exter- 
nal to  the  crus  cerebri,  whence  it  may  be  traced  to  its  deep  or 
real  origin  from  various  parts  of  the  optic  thalamus  and  from 
the  corpora  quadrigemina.  Winding-  around  the  outer  side  of 
the  crus  cerebra,  it  passes  forward  and  inward  beside  the 
tuber  cinereum  and  in  front  of  it  unites  with  its  fellow  to  form 
the  optic  commissure  or  chiasm.  The  portion  extending-  from 
the  orig-in  to  the  optic  chiasm  is  called  the  optic  tract.  From 
the  optic  chiasm  the  two  optic  nerves  diverg-e  anteriorly  to 
enter  the  orbit  through  the  optic  foramina,  each  piercing"  the 
sclerotic  and  choroid  coats  of  the  eye-ball  to  expand  into  the 
retina. 

The  connection  between  the  optic  tract,  chiasm  and  nerve  is 
as  follows:  The  optic  tract  is  composed  of  filaments,  the 
outermost  of  which  pass  into  the  nerve  of  that  side,  while  the 
innermost  curve  over,  throug-h  the  chiasm,  to  form  the  inner- 
most fibres  of  the  opposite  tract,  and  the  middle  fibres  of  the 
tract  of  one  side  pass  through  the  chiasm  to  form  the  middle 
fibres  of  the  nerve  of  the  opposite  side;  and  the  innermost 
fibres  of  one  nerve  pass  through  the  chiasm  and  become  the 
innermost  fibres  of  the  opposite  nerve,  thus  accounting  for  all 
the  filaments. 

The  Third  Nerve. 

The  third  nerve,  or  motor  ocidi,  leaves  the  brain  just  to  the 
outer  side  of  the  crus,  near  the  front  of  the  pons.  The  deep 
origin  can  be  traced  to  the  locus  niger  and  tegmentum.  It 
pierces  the  dura  below  and  to  the  outer  side  of  the  posterior 
clinoid  process.  It  then  passes  forward  lying  in  the  outer 
wall  of  the  cavernous  sinus,  with  the  fourth  and  opthalmic  di- 
vision of  the  fifth  below  and  external  to  it,  and  the  sixth  in- 
ternal and  separating  the  third  from  the  internal  carotid. 
Continuing  its  course  the  nerve  reaches  the  anterior  lacerated 
foramen,  or  sphenoidal  fissure,  and  splits  into  two  divisions. 
Both  divisions  enter  the  orbit,  passing  between  the  two  heads 


462  DESCRIPTIVE  ANATOMY. 

of  the  external  rectus  muscle  and  being-  separated  from  each 
other  by  the  nasal  nerve.  In  the  sphenoidal  fissure  the  third 
lies  on  the  lower  wall  of  the  fissure  with  the  nasal  and  the 
sixth,  the  upper  division  of  the  third  being- most  external,  then 
the  nasal,  lower  division  of  the  third  and  sixth  in  the  order 
named.  The  terminal  branches  are  now  g-iven  off,  the  nerve 
supplyingf  all  the  muscles  of  the  ocular  g-roup  except  the  ex- 
ternal rectus  and  the  superior  oblique.  The  upper  division, 
which  passes  above  the  optic  nerve,  supplies  the  superior  rec- 
tus and  the  levator  palpebrse.  The  lower  division  passes 
beneath  the  optic  nerve  and  supplies  the  inferior  and  internal 
recti  and  the  inferior  oblique. 

While  lying-  in  the  cavernous  sinus  the  nerve  communicates 
with  the  cavernous  plexus.  Sometimes  the  superior  division 
receives  a  communication  from  the  nasal  ;  while  the  branch  to 
the  inferior  oblique  gives  off  the  motor  root  of  the  ciliary 
g-ang-lion.  The  branches  to  the  muscles  enter  on  their  deep 
or  ocular  surface. 

The  Fourth  Nerve. 

The  fourth,  ox  fatheticus,  appears  just  external  to  the  ap- 
parent orig-in  of  the  third  on  the  outer  surface  of  the  crus 
cerebri.  Its  deep  orig-in  is  a  nucleus  on  the  floor  of  the  aque- 
duct of  Sylvius.  After  winding-  around  the  crus  cerebri  the 
fourth  pierces  the  dura  below  the  posterior  clinoid  process 
and  runs  forward  in  the  sinus  with  the  third  above  and  the 
opthalmic  division  of  the  fifth  below  it.  On  reaching-  the 
sphenoidal  fissure  the  fourth  passes  throug-h  that  fissure  at 
its  hig-hest  and  most  internal  point.  On  reaching-  the  orbit  it 
crosses  over  the  orig-in  of  the  levator  palpebrae  and  enters  the 
superior  oblique  on  the  ocular  surface  of  that  muscle.  It 
communicates  with  the  cavernous  portion  of  the  sympathetic 
and  g-ives  off  a  small  and  unimportant  branch  to  the  tentorium. 

The  Fifth  Nerve. 

Theyf/?/^,  or  trifacial  nerve,  appears  just  behind  the  fourth, 
emerg-ing-  from  the  side  of  the  pons.  It  has  its  superficial,  or 
apparent  origin,  by  two  roots  which  spring  from  the  lateral  as- 


THE  CRANIAL  NERVES  .  463 

pect  of  the  pons,  the  anterior,  consisting-  of  two  or  three  bun- 
dles,  beintr  the  motor,   and  the   posterior  the   sensory,   root. 
The  deep  origin  is  from  the  floor  of  the  fourth  ventricle. 

The  two  roots  pass  throug-h  the  dura  just  above  the  internal 
auditory  meatus  and  continue  forward  to  the  apex  of  the  pet- 
rous portion  of  the  temporal  bone,  where  a  g-angliform  enlarg-e- 
ment,  called  the  Gctsserian ganglion,  is  formed  on  the  posterior 
or  sensory  root.  The  motor  root  passes  beneath  the  g^anglion 
of  Gasser  without  being-  connected  with  it. 

The  g"anglion  divides  into  three  branches,  opthalmic,  supe- 
rior maxillary  and  inferior  maxillary.  The  latter  is  joined 
bodily  by  the  small  root  of  the  nerve  and  is,  therefore,  the 
only  one  of  the  three  divisions  possessing  motor  endowments. 
Besides  its  terminal  branches  the  ganglion  gives  off  branches 
to  the  dura  and  middle  fossa  of  the  skull  and  receives  a  com- 
munication from  the  cavernous  plexus. 

The  Opthalmic  Nerve. 

The  opthalmic  branch  passes  forward  and  soon  divides  into 
three  branches,  lachrymal,  frontal  and  nasal,  which  enter  the 
orbit  through  the  foramen  lacerum  anterius.  This  nerve 
passes  through  an  opening  in  the  dura  l^nng  below  and  external 
to  that  for  the  fourth.  It  then  runs  forward  on  the  outer  wall 
of  the  cavernous  sinus,  its  place  being  below  and  to  the  outer 
side  of  the  third  and  fourth.  The  terminal  branches  are  given 
off  just  before  the  nerve  reaches  the  sphenoidal  fissure. 

Branches. 

Lachrymal  Frontal 

Nasal 

The  Lachrymal  branch  of  the  opthalmic  pisses  through  the 
upper,  external  portion  of  the  sphenoidal  fissure  and  enters 
the  orbit  where  it  runs  along  the  external  wall  lying  above  the 
external  rectus  muscle.  It  continues  its  course  until  it  reaches 
the  lachrymal  gland,  which  it  supplies,  and  then  sends  fila- 
ments which  pierce  the  palpebral  ligament  and  are  distributed 
to  the  skin  of  the  upper  eyelid  and  communicates  with  the 
facial  nerve. 


464  DESCRIPTIVE  ANATOMY. 

The  Frontal  is  tHe  largest  branch  of  the  opthalmic  division. 
It  enters  the  orbit  through  the  sphenoidal  fissure,  lying-  be- 
tween the  lachrymal,  externally,  and  the  fourth,  internally. 
It  then  runs  forward  on  the  levator  palpebrae  and  divides  into 
the  supra- trochlear  ?indi.  siipra-orhital. 

The  supra-orhital  emerges  from  the  orbit  through  the  supra- 
orbital foramen,  gives  off  branches  to  the  upper  eyelid  and  the 
muscles  and  integument  of  the  head  as  far  back  as  the  vertex. 
While   lying  in  the   orbicularis  palpebraum,    it  communicates 
with  the  facial  nerve. 

The  supra-trochlear  branch  advances  to  the  inner  angle  of 
the  orbit  where  it  emerges  above  the  fovea  trochlearis,  hence 
its  name,  and  is  distributed  to  the  inner  angle  of  the  eye  and 
the  integument  of  the  root  of  the  nose  and  middle  of  the  fore- 
head. It  gives  a  communicating  branch  to  the  infra-trochlear 
branch  of  the  nasal. 

The  Nasal  Nerve  enters  the  orbit  between  the  heads  of  the 
external  rectus,  lies  beneath  the  superior  oblique  and  the  levator 
palpebr^  crosses  the  optic  nerve,  advances  along  the  inner 
wall  of  the  orbit,  re-enters  the  cranium  through  the  anterior 
ethmoidal  foramen  and  is  there  found  lying  in  the  slit  beside 
the  crista  galli,  whence  it  sinks  into  the  cavity  of  the  nose  and 
divides  into  a  branch  for  the  mucuous  membrane  of  the  nose, 
and  another  to  descend  along  the  posterior  aspect  of  the  nasal 
bone  to  its  lower  edge,  where  it  emerges  through  the  notch 
found  there  and  supplies  the  integument  of  the  nose  to  its  tip. 
Just  as  the  nasal  nerve  is  entering  the  ethmoidal  foramen  it 
gives  off  a  branch  called  the  infra-trochlear,  which  passes  for- 
ward to  emerge  at  the  inner  angle  of  the  orbit  below  the  fovea 
trochlearis  and  supply  the  lachrymal  sac  and  inner  angle  of  the 
eye.  Besides  the  infra-trochlear  it  gives  off  in  the  orbit  three 
other  branches;  one  to  the  opthalmic  g-anglion  of  the  sympa- 
thetic system  and  two  ciliary  branches  which  pierce  the 
sclerotic  coat,  pass  forward  between  it  and  the  choroid  and 
are  distributed  to  the  iris. 

Superior  Maxillary  Nerve. 

The  superior  maxillary  division  of  the  fifth  nerve,  like  the 
opthalmic,  has  a  forward  course.     It  gains  egress  through  the 


THE  CRANIAL  NERVES.  465 

foramen  rotundum,  continues  its  forward  direction  across  the 
spheno-maxillary  fossa,  along- a  g-roove  on  the  floor  of  the  orbits 
sinks  beneath  the  floor  and  emerges  at  the  infra-orbital  foramen 
on  the  face  to  give  sensibility  to  adjacent  parts,  viz:  the  lower 
lid,  cheek,  side  of  the  nose  and  upper  lip. 

Branches. 

Besides  the  terminal  ones,  the  branches  of  the  superior 
maxillary  are  the  following-,  emitted  in  the  order  g*iven: 

The  orbital  or  tem^oro-iualar .hr-a^woh.  enters  the  orbit  throug-h 
the  spheno-maxillary  fissure  and  divides  into  two  branches, 
temporal  and  malar.  The  temporal  branch  enters  the  tempo- 
ral fossa  through  the  outer  wall  of  the  orbit,  while  the  malar 
branch  continues  along-  the  outer  wall  of  the  orbit  to  emerg-e 
on  the  cheek  at  the  outer  angle. 

The  sfiheno-palatine  are  two  branches  of  communication 
which  descend  to  Meckel's  g-ang-lion  of  the  sympathetic  in  the 
spheno-maxillary  fossa. 

The  chief  distribution  of  the  superior  maxillary  is  to  the 
teeth  and  g-ums  of  the  upper  jaw  and  this  is  effected  by  two 
branches,  anterior  and  -posterior  dental.  The  -posterior  dental 
is  first  emitted  and  supplies  the  molar  and  bicuspid  teeth. 

The  anterior  dental  leaves  the  main  trunk  just  as  it  is  about 
to  emerge  on  the  face  and  supplies  the  two  incisors,  the  canine 
and  the  front  bicuspid.  The  anterior  and  posterior  dental 
nerves  anastomose  in  the  bone  and  supply  each  tooth  with  as 
many  filaments  as  the  tooth  has  fangs,  besides  g-iving-  twigs 
to  the  g-ums. 

Inferior  Maxillary  Nerve. 

The  inferior  maxillary  division  of  the  fifth  nerve  consists 
of  a  branch  from  the  gang-lion  of  Gasser  and  the  small  motor 
root  of  tiie  fi  fth  nerve,  which  unite  and  pass  downward  throug-h 
the  foramen  ovale,  immediately  after  emerg-ing  from  which 
the  nerve  divides  into  an  anterior  and  ^.posterior  trunk.  The 
distribution  of  each  trunk  is  as  follows  : 

The  anterior  trunk  breaks  up  into  branches  which  supply 
the  muscles  of  mastication,  each  branch   bearing  the  name  of 

Des  Anat— 30 


466  DESCRIPTIVE  ANATOMY. 

the  muscle  to  which  it  -is  distributed  and  conveying'  motor 
influence. 

The  masseteric  branch  runs  out  above  the  external  ptery- 
goid muscle,  crosses  throug'h  the  sig^moid  notch  and  is  dis- 
tributed to  the  deep  face  of  the  masseter. 

The  deef  temporal  branches  anterior  and  -posterior,  are 
distributed  to  the  deep  face  of  the  temporal  muscles. 

The  buccal  branch  pierces  the  external  pteryg"oid,  some- 
times lying-  beneath  the  coronoid  process  and  sometimes  run- 
ning- through  the  temporal  muscle,  to  be  distributed  by  an 
upper  and  a  lower  branch  to  the  buccinator. 

The  pterygoid  branches  are  one  to  each  pterygoid  muscle  ; 
that  to  the  external  pterygoid  being  frequently  a  branch  of 
the  buccal  nerve. 

The  p>osterior  trunk  divides  into  three  branches,  inferior 
dental,  gustatory  and  auriculo-temporal. 

Inferior  Dental. 

The  inferior  dental  branch  curves  forward  and  downward 
to  enter  the  dental  foramen  of  the  lower  jaw  and  run  along  a 
canal  in  the  bone  giving  filaments  to  all  the  teeth  of  the  lower 
jaw.  It  first  lies  beneath  the  external  pterygoid  muscle  and 
then  between  the  internal  lateral  ligament  and  the  ramus  of 
the  lower  jaw. 

As  it  passes  the  mental  foramen  it  gives  off  a  branch  which 
escapes  through  that  foramen  and  supplies  the  integument  of 
the  lower  lip.  Just  before  entering  the  dental  foramen  the 
nerve  gives  off  a  branch  called  the  ?7iylo-hyoidean,  which  de- 
scends along  the  groove  on  the  inner  surface  of  the  inferior 
maxilla  and  is  distributed  to  the  mylo-hyoid  muscle  and  the 
anterior  belly  of  the  digastric. 

Gustatory  Branch. 

The  gustatory  nerve  passes  downward  and  forward,  first 
behind  the  external  pterygoid  muscle,  then  between  the 
two  pterygoid  muscles  and  then  between  the  internal  pterygoid 
and  ramus  of  the  lower  jaw,  and  reaching  the  side  of  the  tongue 
splits  into   many  filaments  to  supply  the  anterior   part  of  that 


THE  CRANIAL  NERVES.  467 

oro-an.  While  between  the  two  pter^^gfoid  muscles  it  receives 
at  an  acute  angle  the  chorda  tympani  a  branch  of  the  seventh 
nerve,  which  it  transmits  to  the  submaxillary  g-ang-lion  of  the 
sympathetic.  Beneath  the  tono-ue  the  gustatory  gives  off  a 
branch  of  communication  to  the  twelfth. 

It  distributes  branches  to  the  filiform  and  fungiform  papillae, 
the  mucous  membrane  of  the  tongue,  mouth,  and  gums. 

Auriculo-Temporal. 

The  auriculo-temporal  branch  arises  by  two  roots.  It  first 
passes  backward  behind  the  articulation  of  the  lower  jaw, 
then  ascends  between  the  meatus  auditorius  externus  and 
condyle  of  the  lower  jaw  and  emerging  from  beneath  the  paro- 
tid gland  divides  into  branches  called  anterior  and  posterior 
temporal  which  supply  the  integument  of  the  temporal  region. 
It  gives  off  branches  to  the  articulation  of  the  lower  jaw,  to 
the  parotid  gland,  to  the  pinna,  to  the  meatus  auditorius  and 
two  communicating  branches  to  the  facial  nerve. 

Sixth  Nerve. 

The  sixth  nerve ,  or  abducens,  has  its  apparent  origin  from  the 
upper  constricted  portion  of  the  medulla,  just  behind  the  pons, 
while  its  deep  origin  can  be  traced  to  a  mass  of  gray  matter 
lying  in  the  floor  of  the  fourth  ventricle.  The  nerve,  after 
piercing  the  dura  over  the  sphenoid,  runs  through  an  opening 
in  the  dura  just  below  the  posterior clinoid  process  and  passes 
forward  in  the  cavernous  sinus,  lying  internal  to  the  preceding 
nerve  and  in  close  contact  with  the  internal  carotid  artery. 
Continuing  its  course  it  passes  into  the  orbit  through  the 
sphenoidal  fissure  just  external  to  the  opthalmic  vein,  runs 
between  the  two  heads  of  the  external  rectus  and  is  distributed 
to  that  muscle  from  its  deep  surface. 

Seventh  Nerve. 

The  seventh,  or  facial,  nerve  (the  motor  nerve  of  the  face) 
is  the  uppermost  of  the  five  nerves  which  spring  from  the 
groove  between  the  corpora  olivare  and  restiformia.  Its  deep 
origin  is  from  the  floor  of  the  fourth  ventricle,  where  it  com- 
municates with  the  sixth  nerve.     Just  beneath  it,  in  the  same 


468  DESCRIPTIVE  ANATOMY. 

groove,  is  another  nerve  called  the  portio  intermedia  which 
unites  with  it.  If  this  be  counted  as  a  separate  nerve,  it  may  be 
said  that  there  are  six  nerves  spring-ing-  successively  from  this 
groove.  It  makes  for  the  internal  auditory  meatus  which  it 
enters  in  company  with  the  auditory  nerve  ;  and,  when  the 
two  reach  the  bottom  of  the  canal,  the  facial  parts  from  its 
companion  and  enters  another  canal  in  the  petrous  bone  called 
the  aqueduct  of  Pallopius,  which  conducts  it  first  outward, 
then  backward  and  then  downward  to  the  stylo-mastoid  fora- 
men, emerg-ing-  from  which  it  passes  forward  through  the 
parotid  g-land,  over  the  external  carotid  artery,  and  divides 
into  numerous  branches  which  are  distributed  to  all  the  mus- 
cles of  the  face  except  those  of  mastication,  and  of  these  the 
buccinator  g-ets  a  branch. 

Branches. 

Ivike  other  cranial  nerves,  its  branches  may  be  divided  into 
two  sets,  viz  :  communicating'  and  branches  of  distribution. 
While  in  the  auditory  meatus,  it  communicates  with  the  audi- 
tory nerve.  In  the  aqueductus  Fallopii  the  larg-e  su-perficial 
petrosal  is  sent  to  Meckel's  g-ang-lion,  the  small  -petrosal  to 
the  otic  g^ang-lion  and  the  external  petrosal  to  the  sympathetic 
on  the  middle  meing-eal  artery.  After  the  nerve  emerg-es 
from  the  stylo-mastoid  foramen,  communications  are  estab- 
lished with  the  ninth  and  tenth  cranial  nerves,  with  the  caro- 
tid plexus,  with  the  auricularis  magnus  of  the  cervical  plexus 
and  with  the  auriculo-temporal  branch  of  the  fifth.  All  of  the 
divisions  of  the  fifth  communicate  with  the  seventh  on  the 
face. 

The  branches  of  distribution  the  tympanic  and  chorda  tym- 
■pani,  arising"  within  the  aqueductus  Fallopii  ;  the  posterior 
auricular,  stylo-hyoid  and  dig-astric  arising-  outside  the  stylo- 
hyoid foramen,  and  two  terminal  branches,  the  temporo-facial 
and  cervico-i?i.QA'al. 

The  tympanic,  which  arises  from  the  facial  while  it  is  in 
the  aqueduct  of  Fallopius  and  is  distributed  to  a  muscle  of  the 
tympanic  cavity. 

The  chorda  tympani,  which  is  emitted  from  the  facial  just 


THE  CRANIAL  NERVES.  469 

above  the  stylo-mastoid  foramen  and  first  ascends  throug"h 
the  petrous  bone  and  enters  the  tympanum  at  the  base  of  the 
pyramid  on  its  posterior  wall,  then  crosses  on  the  inner  surface 
of  the  membrana  tympani  and  leaves  throug"h  the  fissure  of 
Glaser,  having-  emerged  from  which  it  joins  the  gustatory 
branch  between  the  two  pteryg-oid  muscles  and  continues  with 
it  to  the  submaxillary  g-ang-lion. 

The  stylo-hyoid  which  supplies  the  stylo-hyoid  muscle. 

The  digastric,  which  is  distributed  to  the  posterior  belly  of 
the  dig-astric  muscle. 

The  posterior  auricular,  which  ascends  behind  the  ear  and 
after  communicating"  with  the  auricular  branch  of  the  pneumo- 
gastric  is  distributed  by  an  anterior  branch  to  the  auricle  and 
by  a  posterior  to  the  back  of  the  head. 

The  temporo-facial \^  the  larg-er  of  the  two  terminal  branches 
of  the  seventh.  It  passes  throug-h  the  parotid  gland,  which 
separates  it  from  the  external  carotid  artery,  and  breaks  up 
into  three  sets  of  branches,  temporal,  malar  and  infra-orbital, 
the  first  supplying-  the  attrahens  aurem,  occipito-frontalis  and 
orbicularis  palpebraum  muscles;  the  second  the  orbicularis  and 
corrug-ator  supercillii,  while  the  last,  the  largest  branch,  sup- 
plies the  pyramidalis  nasi,  levator  labii  superioris  and  levator 
anguli  oris. 

The  cervico-facial d\v'\'^\ovL  passes  downward  in  the  substance 
of  the  parotid  gland,  which  separates  it  from  the  external 
carotid.  It  communicates  with  the  auricularis  magnus  and 
divides  into  <^2^cc«/ branches,  which  supply  the  buccinator  and 
orbicularis  oris;  supra-maxillary  for  the  depressor  anguli  oris; 
and  infra-maxillary,  some  of  which  supply  the  platysma  while 
others  pass  to  the  skin  over  the  supra-hyoid  region,  communi- 
cating with  the  branches  of  the  cervical  plexus  in  that  region. 

Eighth  Nerve. 

The  eig-Jith  nerve,  or  portio  mollis,  or  auditory,  is  the  sec- 
ond of  the  nerves  arising  from  the  groove  between  the  corpora 
olivare  and  restiforme,  its  deep  origin  being  from  the  floor  of 
the  fourth  ventricle.  It  passes  forward  and  enters,  along 
with  the  seventh,  the  internal  auditory  meatus,  at  the  bottom 


470  DESCRIPTIVE  ANATOMY. 

of  which  it  divides  into  a  cochlear  and  three  vestibular  branches, 
which  are  distributed  to  corresponding-  parts  of  the  labyrinth. 

Ninth  Nerve. 

The  ninth  nerve,  or  g-losso-fharyngeal,  is  the  third  nerve 
arising"  in  the  g-roove  between  the  corpora  olivare  and 
restiforme.  Its  deep  orig-in  is  from  the  floor  of  the  fourth 
ventricle  between  the  eig^hth  and  tenth.  It  escapes  from  the 
cranium,  along-  with  the  tenth  and  eleventh,  throug"h  the  pos- 
terior foramen  lacerum,  lying-  behind  the  internal  carotid 
artery  ;  it  then  passes  forward  between  the  artery  and  the  in- 
ternal jug-ular  vein  to  the  outer  side  of  the  artery,  then  crosses 
the  artery  in  front  of  the  posterior  border  of  the  stylo- 
pharyngeus,  and  then  crosses  that  muscle  to  be  distributed  by 
its  terminal  filaments  to  the  mucous  membrane  of  the  poste- 
rior part  of  the  tong-ue. 

This  nerve  presents  two  g-ang-liform  enlargements  called 
superior,  or  jug'ular,  and  inferior,  ov  petrous.  The  superior 
which  is  very  small,  is  situated  in  the  jug-ular  foramen  and 
does  not  involve  all  the  fibres  of  the  nerve.  The  inferior 
g-ang-lion  is  situated  in  a  depression  on  the  posterior  border  of 
the  petrous  portion  of  the  temporal  bone  and  g-ives  off  branches 
of  cummunication  to  the  pneumog-astric  and  sympathetic. 

Branches. 

Besides  its  terminal  branches  the  ninth  nerve  g-ives  off  four 
branches  of  distribution. 

The  tympanic  branch,  Jacohson  s  nerve,  passes  to  the  tym- 
panum throug-h  a  canal  which  opens  on  the  ridg-e  of  bone  be- 
tween the  carotid  and  jug-ular  foramina.  After  reaching-  the 
tympanum  it  is  distributed  by  six  branches,  as  follows: 

{(i)  One  to  the  lining-  membrane  of  the  tympanum  and  E^usta- 
chian  tube. 

(^)  One  to  the  fenestra  rotunda. 

{c)  One  to  the  fenestra  ovalis. 

{d)  One  to  the  carotid  plexus  of  the  sympathetic. 

{e)  One  to  the  g-reat  superficial  petrosal  nerve. 
(_/)  One  to  the  lesser  superficial  petrosal  nerve. 


THE  CRANIAIv  NERVES.  471 

A  muscular  branch   which   supplies  the  stylo-pharyngeus. 

The  ■pharyngeal  branches,  which  are  found  on  the  poste- 
rior part  of  the  pharynx  aiding-  to  form  a  plexus  called  the 
pharyngeal  from  which  the  pharynx  is  supplied.  The  other 
nerves  antering- into  the  formation  of  this  plexus  are  the  phary- 
geal  and  superior  laryngeal  of  the  tenth  and  the  sympathetic. 

The  tonsillar  branches  which  form  a  plexus  on  the  tonsils. 

The  branches  of  communication  of  the  ninth  nerve  are  as 
follows: 

One  to  the  gangflion  of  the  tenth  nerve. 

One  to  the  superior  cervical  ganglion   of  the  sympathetic. 

One  to  the  seventh  nerve. 

Carotid   filaments   which  descend   with  the  carotid  artery. 

Tenth  Nerve. 

The  tenth  nerve,  or  pneiunog'astric,  or  par  vag'um,  is  the 
fourth  nerve  arising  from  the  g-roove  between  the  corpora 
olivare  and  restiforme.  It  escapes  from  the  cranium  through 
the  jugular  foramen  and,  descending  the  neck,  enters  the  thorax 
through  which  it  passes  along  with  the  oesophagus  and  gains 
the  abdomen  where  it  is  found  running  from  left  to  rig-ht  along 
the  lesser  curvature  of  the  stomach.  In  the  neck  the  course 
and  relations  of  the  nerve  are  the  same  on  both  sides,  /.  <?.,  the 
nerve  lies  first  between  the  internal  jugular  vein  and  the  in- 
ternal carotid  artery,  then  between  the  internal  jugular  vein 
and  common  carotid  artery  until  it  reaches  the  root  of  the  neck 
and  the  relations  thenceforward  vary  according-  to  the  side. 
The  rig-ht  nerve  at  the  root  of  the  neck  crosses  the  first  portion 
of  the  subclavian  artery,  enters  the  chest,  reaches  the  posterior 
aspect  of  the  root  of  the  right  lung;  descends  thence  along  the 
posterior  aspect  of  the  (esophagus  to  the  stomach  and  runs 
along  the  lesser  curvature  of  that  organ,  being  distributed  by 
its  terminal  filaments  to  its  posterior  face.  The  left  enters 
the  thorax  lying  on  the  front  of  the  first  portion  of  the  left 
subclavian,  crosses  the  front  of  the  arch  of  the  aorta,  reaches 
the  posterior  aspect  of  the  root  of  the  left  lung  and  thence 
passes  down  the  front  of  the  oesophagus  to  the  stomach,  runs 
alonL*"  its  lesser  curvature  and  is  distributed  to  its  anterior  face. 


472  DESCRIPTIVE  ANATOMY. 

While  in  the  jug-ular  foramen  the  nerve  presents  a  gang-liform 
enlargement  called  the  ganglion  of  the  root,  and  about  half  an 
inch  below  this  a  second  and  larger  one  called  the  ganglion  of 
the  trunk. 

Branches. 

The  branches  are  divided  into  commiinicating  and  branches 
of  distribution.  The  communicating  are  mainly  connected 
with  the  two  ganglia  on  the  nerve.  The  gang-lion  of  the  root 
receives  branches  from  the  accessory  portion  of  the  spinal  ac- 
cessory, the  petrous  ganglion  of  the  ninth,  the  auricular  branch 
of  the  facial  and  from  the  superior  cervical  of  the  sympathetic. 

The  g-ang-lion  of  the  trunk  is  connected  with  the  twelfth, 
the  superior  cervical  ganglion  of  the  sympathetic  and  with  the 
loop  between  the  first  and  second  cervical. 

The  branches  of  distribution  are 

Auricular  Thoracic  Cardiac 

Pharyngeal  Anterior  Pulmonary 

Superior  Laryngeal  Posterior  Pulmonary 

Recurrent  Laryngeal  (Ksophageal 

Cervical  Cardiac  Gastric 

Of  these  branches  the  first  arises  in  the  jugular  fossa,  the 
next  four  in  the  neck  and  the  remainder,  except  the  gastric, 
which  comes  off  in  the  abdomen,  in  the  thorax. 

The  auricular,  or  Arnold' s  nerve,  is  a  small  branch  which 
springs  from  the  ganglion  of  the  root.  Passing  through  a 
small  canal  in  the  jugular  fossa  it  runs  through  the  petrous 
portionof  the  temporal,  where  it  communicates  with  the  facial, 
leaves  the  temporal  through  the  auricular  fissure  and  is  dis- 
tributed to  the  back  of  the  pinna,  communicating  with  the 
auricularis  magnus. 

The.  pharyngeal  branch  arises  from  the  ganglion  of  the  root 
and  descends  to  the  posterior  aspect  of  the  pharynx  to  aid  in 
forming  the  pharyngeal  plexus.  It  passes  across  the  internal 
carotid,  usually  behind  to  the  upper  edge  of  the  middle  con- 
strictor where  it  breaks  up  into  branches.  It  receives  its  motor 
fibres  probably  from  the  eleventh  and  communicates  with  the 
ni  ith,  superior  laryngeal  and  the  sympathetic  to  form  the 
pharyngeal  plexus. 


THE  CRANIAL  NERVES.  473 

The  superior  laryngeal  branch  arises  from  the  g-ang-liou  of 
the  trunk  and  descending-  pierces  the  thyro-hyoid  membrane 
and  is  distributed  to  the  mucous  membrane  of  the  larynx,  g-iving- 
a  filament  to  the  arytenoid  muscle.  Just  below  the  thyro- 
hyoid membrane  it  g-ives  off  a  branch  called  the  external 
laryngeal,  which  is  distributed  to  the  thyroid  g-land  and  crico- 
thyroid muscle  and  furnishes  some  filaments  to  the  pharyng-eal 
plexus. 

This  nerve  receives  a  communication  from  the  eleventh  and 
afterward  communicates  with  the  recurrent  laryng-eal  and  with 
the  pharyng-eal  plexus.  In  its  course  down  the  neck  it  lies 
bv  the  side  of  the  pharynx  and  crosses  behind  the  internal 
carotid  artery. 

The  recurrent  or  inferior  laryng-eal  branch  arises  at  a  differ- 
ent point  on  each  side;  on  the  left  it  arises  as  the  pneumog-as- 
tric  is  crossing-  the  aorta  and  winds  backward  around  the 
aorta;  on  the  rig-ht  it  arises  as  the  nerve  is  crossing  the  first 
portion  of  the  subclavian  and  winds  around  that  artery.  After 
passing-  around  the  aorta  (or  subclavian,  as  the  case  may  be) 
each  nerve  ascends  in  the  groove  between  the  trachea  and 
oesophagus,  giving-  filaments  to  those  parts,  and  is  distributed 
to  all  the  muscles  of  the  larynx  except  the  crico-thyroid. 

Each  nerve  gives  off  cardiac  branches  which  unite  with  those 
from  the  sympathetic  and  tenth  to  form  the  cardiac  plexuses. 
There  are  more  oesophageal  branches  given  off  from  the  right 
than  from  the  left  nerve.  Other  branches  supply  the  mucous 
membrane  of  the  trachea  and  some  branches  pass  to  the  infe- 
rior constrictor. 

The  cervical  cardiac  branches  are  divided  into  superior  and 
inferior.  The  superior  usually  join  the  great  cardiac  plexus, 
as  does  the  inferior  on  the  right.  The  left  inferior  goes  gen- 
erally to  the  superficial  plexus. 

The  thoracic  cardiac  branches  come  entirely  from  the  right 
nerve  (all  the  left  thoracic  coming  from  the  recurrent  laryngeal) 
and  pass  to  the  deep  plexus. 

The  -posterior pulmonary  branches  form  an  intricate  plexus 
on  the  back  of  the  root  of  the  lung,  whence  filaments  are 
sent  along  the  bronchial  tubes  into  the  lungs. 


474  DESCRIPTIVE  ANATOMY. 

The  anterior  -pulmonary  branches  form  a  smaller  plexus 
on  the  front  of  the  root  of  the  lung-. 

The  oesophageal  branches  are  filaments  furnished  the 
oesophag-us  before  the  nerves  are  in  relation  with  it. 

The  two  nerves  communicate  frequently  around  the  tube, 
surrounding-  it  with  numerous  anastomoses,  thus  forming-  the 
oesophag-eal  plexus. 

The  g-astric,  or  ter^nmal,  branches  are  distributed  to  both 
faces  of  the  stomach,  the  rig-ht  nerve  g'oing-  to  the  back,  and 
the  left  to  the  front,  of  that  org-an.  The  two  communicate 
with  each  other  and  with  the  caeliac,  splenic,  and  hepatic 
plexuses. 

Eleventh  Merve. 

The  eleventh  nerve,  or  spinal  accessory,  is  the  fifth  nerve 
arising-  in  the  g-roove  between  the  corpora  olivare  and  resti- 
forme  and  escapes  from  the  cranium  throug-h  the  posterior 
foramen  lacerum  along-  with  the  ninth  and  tenth  nerves.  The 
nerve  consists  of  two  portions:  1st,  a  cranial  or  accessory  por- 
tion which  arises  from  the  g-roove  mentioned  and,  after  com- 
municating- with  the  cervical  portion,  g-oes  to  the  pneumog-as- 
tric  ;  2d,  a  spinal  portion  which  arises  by  successive  filaments 
from  the  side  of  the  spinal  cord  as  low  as  the  sixth  cervical 
nerve  and  ascends  between  the  two  roots  of  the  spinal  nerves. 
It  enters  the  cranium  throug-h  the  foramen  mag-num  and  after 
communicating-  with  the  accessory  portion  emerg-es  through 
the  jug-ular  foramen,  passes  downward  and  outward,  pierces 
the  sterno-cleido-mastoid  muscle  and  reaches  the  trapezius  to 
which  it  is  distributed,  g-iving-,  on  its  way,  filaments  to  the 
sterno-cleido-mastoid.  The  two  portions  of  this  nerve  are 
never  closely  united,  but  after  the  spinal  portion  has  ascended 
to  the  cranium  several  communicating-  branches  pass  between 
them. 

Twelfth  Nerve. 

The  twelfth  nerve,  or  hypoglossal,  arises  from  the  g-roove 
between  the  corpora  olivare  and  pyramidale  by  ten  or  twelve 
filaments  which  are  g-athered  into  two  bundles  :  these  pass 
outward  and,   just   as  they  are    leaving-  the  cranium  throug-h 


THE  CRANIAL  NERVES  475 

the  anterior  condyloid  foramen,  unite  to  form  the  trunk  of  the 
nerve.  The  nerve  then  descends  between  the  internal  jugu- 
lar vein  and  internal  carotid  artery  and,  w^hen  it  reaches  a 
point  on  a  level  with  the  jaw,  curves  forward  in  front  of  both 
internal  and  external  carotid  arteries,  and  after  communica- 
ting- with  the  gustatory  nerve  is  distributed  to  the  muscles  of 
the  tongue. 

Branches. 

The  branches  of  distribution,  besides  the  terminal,  are  two, 
the  descendens  noni,  a  very  important  branch,  and  the  thyro- 
hyoidean  of  small  importance. 

The  descendens  noni  leaves  the  hypoglossal  just  as  it  is 
crossing  the  external  carotid  artery  and  derives  its  name  from 
its  direction  and  from  the  fact  that  the  twelfth  nerve  was,  in 
Willis'  classification,  called  the  ninth.  It  passes  down  the 
neck  on  the  front  of  the  sheath  of  the  external,  carotid  artery, 
and  then  on  the  sheath  of  the  common  carotid,  occasionally 
descending  in  the  sheath.  About  the  middle  of  the  neck  it 
anastomoses  with  filaments  from  the  second  and  third  cer- 
vical nerves,  the  communicans  noni,  forming  what  is  called 
the  arch  of  Scarpa,  which  lies  in  front  of  the  sheath  of  the  com- 
mon carotid  artery  about  the  middle  of  the  neck.  From  this 
arch  branches  are  given  to  the  depressor  muscles  of  the  hyoid 
bone,  except  the  thyro-hyoid. 

The  thyro-hyoidean  branch  descends  from  near  the  termination 
of  the  hypoglossal  nerve  to  supply  the  thyro-hyoid  muscle. 


476  DESCRIPTIVE  ANATOMY. 


THE  SYMPATHETIC  NERVES. 

The  sympathetic  nervous  system  consists  of  a  vertebral  and 
a  cranial  portion. 

The  Vertebral  Portion. 

The  vertebral  -portion  of  the  sympathetic  consists  of  two 
similar  series  of  gfang-lia,  lyinof  one  on  each  side  of  the  verte- 
bral column,  extending-  from  the  skull  to  the  coccyx,  and  the 
nerves  which  are  connected  with  these  g^anglia.  Of  these 
gang-lia  there  are  about  twenty-four  divided  into  cervical,  of 
which  there  are  three,  dorsal,  of  which  there  are  twelve,  lumbar, 
of  which  there  are  four  or  five  and  sacral,  of  which  there  are 
about  four.  I)ach  gang-lion  is  provided  with  four  sets  o  f 
branches:  1st,  ascending  to  connect  it  with  the  ganglion  above; 
2d,  descending  to  connect  it  with  the  ganglion  below;  3rd, 
external  to  connect  it  with  the  contiguous  spinal  nerve;  4th, 
internal  or  branches  of  distribution.  The  first  three  sets  of 
branches  are  the  communicating  branches,  and  each  of  the 
connections,  viz:  with  the  ganglion  above,  the  ganglion  below 
and  the  spinal  nerves,  is  affected  by  two  filaments,  one  of  which 
is  gray  and  the  other  white.  The  fourth  set  of  branches,  the 
internal  or  distributing,  pass,  as  a  rule,  inward  and  forward 
to  supply  the  organs  of  their  various  regions;  these  branches 
going  either  singly  to  their  destination, .or,  as  in  some  cases, 
several  branches  from  one  side  meet  similar  ones  from  the 
opposite  side  and  communicating  with  them  on  the  front  of  the 
vertebral  column,  form  plexuses  from  which  the  branches  of 
distribution  proceed.  Three  of  these  plexuses  exist,  known 
as  the  cardiac,  solar  and  hypogastric,  these  constituting  what 
is  called  the  prevertebral  sympathetic.  As  a  rule  each  gang- 
lion is  connected  with  but  one  spinal  nerve,  but  to  this  there 
are  exceptions,  which  will  be  found  in  the  cervical  portion. 

Cervical  Portion. 

The  cervical  -portion  of  the  sympathetic  is  that  part    of  the 
chain  or  trunk  which  is  found  in  the  cervical  region.  Although 


THE  SYMPATHETIC  NERVES.  477 

there  are  eig-ht  cervical  spinal  nerves,  there  are  only  three 
sympathetic  g^anglia,  known  respectively  as  superior,  middle 
and  inferior. 

The  Superior  Cervical  Ganglion. 

The  Superior  Cervical  Ganglion  lies  on  the  front  lateral 
aspect  of  the  second  and  third  cervical  vertebrae,  is  fusiform  in 
shape,  varies  in  size,  and  is  found  to  be  seg^mented  so  as  to 
correspond  to  the  four  upper  cervical  vertebrae.  It  receives 
communications,  by  means  of  its  external  branches,  from  the 
first,  second,  third,  and  fourth  cervical  nerves,  and  also  smaller 
branches  from  the  g-losso-pharyngeal,  pneumogfastric,  and 
hypo-gflossal  nerves.  This  trang*lion  being-  situated  between 
the  spinal  and  cranial  nerves,  receives  communications  from 
both  sets. 

It  lies  directly  behind  the  internal  carotid  artery  ;  and  the 
cord  which  connects  it  with  the  middle  cervical  g-anglion  passes 
downward  behind  the  common  carotid  artery,  resting  upon 
the  prevertebral  g-roup  of  muscles. 

Its  ascending-  branches  pass  along  the  internal  carotid 
artery  and  are  divided  into  two  sets  of  branches,  one  entering- 
into  the  formation  of  the  cavernous  and  the  other  into  the 
carotid  plexus.  The  descending-  branches,  white  and  gray, 
connect  it  with  the  middle  cervical  gfang-lion. 

Its  branches  of  distribution  are  three  in  number,  viz.,  the 
pharyng-eal,  which  unite  with  branches  of  the  g-losso-pharyn- 
g-eal  and  pneumogastric  nerves,  and  with  them  form  a  plexus 
situated  on  the  posterior  wall  of  the  pharynx,  which  divides 
into  numerous  minute  twigs,  distributed  to  the  muscles,  blood- 
vessels, and  glands  of  that  organ.  The  laryngeal  brandies 
unite  with  the  superior  laryng-eal  branch  of  the  pneumog-astric, 
and  form  a  plexus  distributed  to  the  larynx.  The  last  branch 
is  given  to  the  heart,  and  is  called  the  superior  cardiac,  to 
distinguish  it  from  smaller  branches  derived  from  the  middle 
and  inferior  cervical  g-anglia.  This  is  a  long-,  slender  nerve, 
which  passes  down  the  neck  behind  the  common  carotid  artery, 
crossing-  on  the  rig-ht  side,  sometimes  behind,  sometimes  in 
front  of  the  first  portion  of  the  subclavian  artery,  while  on 


478  DESCRIPTIVE  ANATOMY. 

the  left  side  it  passes  behind  the  thoracic  portion  of  the  sub- 
clavian. The  nerve  then  enters  the  thoracic  cavity.  On  the 
right  side  it  joins  with  the  great  deep  cardiac  plexus,  while 
on   the   left  side  it  unites    with  the   g-reat  superficial  cardiac 

plexus. 

The  Middle  Cervical  Ganglion. 

The  Middle  Cervical  Gang-lion  is  situated  opposite  the 
fiftn  cervical  vertebra,  is  very  small  in  size,  and  is  frequently 
entirely  absent. 

Its  superior  branch  communicates  with  the  upper  cervical 
gangiion,  its  inferior  branch  with  the  lower,  while  its  external 
branches  correspond  to  the  fifth  and  sixth  cervical  nerves. 

Its  internal  branches  or  branches  of  distribution,  are  the 
middle  cardiac  and  thyroid. 

The  thyroid  passes  over  the  inferior  thyroid  artery  just 
at  the  point  at  which  it  makes  its  bend  to  turn  inward  towards 
the  thyroid  gland;  and  commumicating  with  the  superior  car- 
diac and  a  branch  of  the  recurrent  and  external  laryngeal 
nerves,  it  is  distributed  to  the  thyroid  body. 

The  middle  cardiac  nerve,  the  largest  of  the  three  cardiac 
branches,  arises  either  from  the  middle  cervical  ganglion  or 
from  the  cord  between  that  ganglion  and  the  superior.  It 
passes  down  the  neck  behind  the  common  carotid  artery,  and 
at  the  root  of  the  neck  the  right  nerve  passes  sometimes  in  front 
and  sometimes  behind  the  subclavian  artery,  descends  upon 
the  trachea,  and,  after  receiving  filaments  from  the  recurrent 
laryngeal  nerve,  joins  the  great  deep  cardiac  plexus.  On  the 
left  side  it  enters  the  chest  between  the  left  common  carotid 
and  the  subclavian  arteries,  and  joins  the  deep  cardiac  plexus. 

The  Inferior  Cervical  Ganglion. 

The  Inferior  Ganglion  is  situated  between  the  base  of  the 
transverse  processes  of  the  last  cervical  and  the  first  dorsal 
vertebrse.  It  is  probably  the  product  of  the  last  two  cervical 
nerves,  the  two  ganglia  having  coalesoed  to  form  a  single  one. 
It  is  not  infrequently  blended  with  the  first  thoracic  ganglion. 

Its  ascending  fibres  communicate  with  the  middle  cervical, 
and  its  lower,  or  descending  fibres  with  the  first  dorsal  gang- 
lion, when  that  ganglion  fails  to  coalesce  with  the  last  cervical. 


THE  SYMPATHETIC  NERVES.  479 

Its  exteriml  fibres  are  derived  from  the  last  two  cervical 
nerves,  the  seventh  and  eigfhth,  while  its  internal  brunch  is 
the  last  of  the  three  cardiac  nerves.  It  communicates  with 
the  recurrent  laryng-eal  and  middle  cardiac  nerve;  and  then 
passing-  into  the  thoracic  cavity,  unites  with  the  deep  cardiac 
plexus. 

The  Cardiac  Nerves. 

It  vt^ill  be  seen  that  there  are  two  larg"e  plexuses  connected 
with  the  heart  and  supplying-  the  muscular  fibres  of  that  org-an. 
These  are  known  as  the  ^;'e«/  deep  cardiac  plexus  and  the 
superficial  cardiac  plexus. 

The  Superficial  Portion  is  found  lying-  on  the  ductus  arte- 
riosus, and  is  the  product  of  the  superior  cardiac  nerve  of  the 
left  side  and  the  inferior  cervical  cardiac  branch  of  the  pneu- 
mogastric. 

The  Deep  Plexus,  situated  in  the  bifurcation  of  the  trachea, 
is  formed  by  the  three  cardiac  nerves  of  the  rig-ht  side  and  the 
middle  and  the  inferior  cardiac  nerves  of  the  left  side. 

Thus  it  is  seen  that  only  two  cardiac  nerves  enter  the  super- 
ficial plexus,  viz;  the  left  superior  cardiac  from  the  sympathetic 
and  the  inferior  cervical  cardiac  branch  from  the  left  pneumo- 
g-astric;  while  the  deep  cardiac  plexus  is  formed  by  the  three 
rig-ht  cardiac  branches  from  the  sympathetic,  the  left,  middle 
and  lower  sympathetic,  and  the  cardiac  branches  of  the  rig-ht 
pneumog-astric. 

From  these  two  plexuses  branches  proceed,  which  following 
the  course  of  the  coronary  arteries,  are  distributed  along-  these 
vessels  to  the  muscular  coats  of  the  vessels  themselves  and  to 
the  fibres  of  the  heart. 

The  Thoracic  Portion  of  the  Sympathetic. 

The  Thoracic,  or  Dorsal,  Sympathetic  consists  of  twelve 
g-ang-lia  on  either  side  of  the  body,  corresponding-  to  the  number 
and  position  of  the  dorsal  vertebrae.  These  g-ang-lia  are  uni- 
fcjrmly  arrang-ed,  and  consist,  like  other  sympathetic  g-ang-lia, 
of  ascending-  branches  communicating-  with  the  g-ang-lion  above, 
descending-  branches  communicating-  with  the  g-anglion  below, 
external,   which  are  usually   two  branches  and  communicate 


480  DESCRIPTIVE  ANATOMY. 

with  the  corresponding-  dorsal  nerves,  and  internal  which  are 
branches  of  distribution. 

The  Branches  of  Distribution,  coming-  from  the  dorsal 
sympethetic  are  almost  entirely  confined  to  the  abdominal 
cavity.  They  form  three  nerves,  known  as  \)a^  greater,  lesser, 
and  least  S-planchnic. 

The  internal  branches  of  the  g-angflia  are  divided  into  two 
sets  :  the  upper  and  small  ones  are  distributed  along-  the 
branches  of  the  thoracic  aorta  ;  w^hile  of  the  lower  ones,  those 
between  the  sixth  and  tenth  g-ang-lia  unite  to  form  the  great 
sflanclmic  nerve,  the  tenth  and  eleventh  gfanglia  form  the 
lesser  splanchnic,  and  the  leasj:,  or  renal,  splanchnic  is  the 
product  of  the  twelfth. 

The  Great  Splanchnic  Nerve  passes  down  the  front  of  the 
vertebral  column  behind  the  peritoneum,  pierces  the  corre- 
sponding- crus  of  the  diaphrag-m,  and  enters  into  the  semi-lunar 
g-ang-lion  of  its  side. 

The  Lesser  Splanchnic  Nerve,  the  product  of  the  tenth  and 
eleventh  g-ang-lia,  also  pierces  the  crus  of  the  diaphrag-m.  and 
joins  with  the  coeliac  plexus  ;  while  the  smallest,  or  least 
Splanchnic  terminates  in  the  renal  plexus. 

The  SeTni-lunar  Ganglia,  found  on  either  side  of  the  coeliac 
axis,  is  apparently  an  enlarg-cment  of  the  g-reater  splanchnic 
nerve.  Each  g-ang-lion  g-ives  off  branches  which  communicate 
with  the  g-ang-lion  of  the  opposite  side,  forming-  a  complete 
net-work  surrounding-  the  lateral  and  anterior  aspects  of  the 
abdominal  aorta,  and  completely  enveloping-  the  coeliac  axis. 
These  numerous  branches  are  collectively  known  as  the  Solar 
Plexus  of  Nerves. 

From  this  solar  plexus  larg-e  branches  follow  the  three 
arteries  into  which  the  coeliac  axis  divides ;  and,  formings 
plexuses  along-  the  course  of  these  vessels,  known  as  the  Gas- 
tric, Hepatic,  and  Splenic  Plexuses,  are  distributed  to  the 
org-aus  which  these  vessels  supply  and  to  the  coats  of  the 
vessels  themselves. 

The  Lesser  Splanchnic,  after  piercing-  the  diaphrag-m,  enters 
into  the  coeliac  plexus;  and  some  of  its  branches  accompany 
the  ramifications  of  the  arteries    mentioned  above,  while  other 


THE  SYMPATHETIC  NERVES.  481 

■filaments  descend  to  the  renal  plexus,  where  that  communicates 
with  the  least  splanchnic  nerve. 

The  Least  Splcaic/niic,  after  piercing-  the  diaphrag-m,  enters 
into  the  formation  of  the  renal  plexus,  from  which  branches 
pass  to  the  kidney  and  to  the  renal  artery  and  vein. 

In  addition  to  the  filaments  accompanying"  the  branches  of 
the  coeliac  axis,  the  solar  plexus  also  gives  off  branches  which 
accompany  the  phrenic,  superior  mesenteric,  spermatic  (or 
ovarian  in  the  female),  and  inferior  mesenteric  branches  of  the 
abdominal  aorta;  and  are  distributedalong  with  these  numerous 
branches.  In  addition  to  these  certain  fibres  also  accompany 
the  aorta  to  form  the  Aortic  Plexus  of  Nerves,  which  after 
communicating  with  the  inferior  mesenteric  plexus,  passes 
over  the  pelvic  brim,  and  aids  in  forming*  a  plexus  on  the  front 
of  the  sacrum,  which  is  called  the  Hypogastric.  From  this 
branches  proceed,  which  are  united  over  the  coccyx  to  form 
the  Ganglion  Inipar,  or  terminal  ganglion  of  the  sympathetic 
system. 

The  Lumbar  Portion  of  the  Sympathetic. 

The  Lumbar  Portion  of  the  Sympathetic  System  is  contin- 
uous above  with  the  dorsal  by  means  of  the  branch  which 
passes  from  the  last  dorsal  sympathetic  g^ang-lion  beneath  the 
ligamentum  arcuatum  to  the  first  lumbar.  The  lumbar 
ganglia  vary  in  number,  being  from  three  to  five. 

They  receive  their  branches  of  communication  from  the 
lumbar  spinal  nerves,  a  descetiding  branch  of  communication 
from  the  ganglion  above,  and  give  a  communicating-  bra)/ch  to 
the  ganglion  below.  These  ganglia  lie  along  the  inner  side 
of  the  psoas  magnus  muscle,  where  they  receive  communicating- 
branches  from  the  lumbar  nerves. 

Of  the  internal  brandies  of  this  plexus  there  are  two  sets. 
The  upper  set  passes  to  the  front  of  the  abdominal  aorta,  and 
forms  there  the  Aortic  Plexus,  which  receives  branches  of 
communication  from  the  solar  plexus  and  from  the  semi-lunar 
ganglion. 

This  plexus  lies  between  the  origin  of  the  superior  and  the 
inferior  mesenteric  arteries,  and  gives  off  branches  to  the  in- 

Des  An  at — 31 


482  DESCRIPTIVE  ANATOMY. 

ferior  mesenteric  and  the  spermatic  arteries  and  to  the  inferior 
vena  cava. 

The  lower  internal  brmiches  enter  into  the  formation  of  the 
hypogastric  plexus,  which  is  situated  on  the  promontory  of  the 
sacrum  between  the  common  iliac  vessels,  and  from  which- 
branches  are  given  off  to  supply  the  pelvic  viscera,  communi- 
cating wath  ganglia  which  correspond  to  the  sacral  nerves. 

Smaller  branches  are  often  given  off  from  the  sacral  nerves 
which  unite  to  form  the  so-called  Pelvic  Plexus.  This  plexus, 
after  distributing  branches  to  the  lower  pelvic  viscera,  corre- 
sponding to  the  arteries  which  pass  to  them,  the  branches 
being  the  Inferior  Hemorrhoidal,  Vesical,  and  Prostatic  in  the 
male,  and  Vaginal -aM^  Uterine  in  the  fem^de,  finally  terminates 
by  uniting  over  the  mid-line  of  the  body  to  form  the  Ganglion. 
Impar,  or  termination  of  the  sacral  plexus  of  nerves. 

The  Cranial  Sympathetic. 

The  cranial  portion  of  the  sympathetic  consists  of  four 
ganglia,  lying  in  and  around  the  skull,  with  their  branches  of 
communication  and  distribution,  and  of  the  carotid  and  caver- 
nous plexuses  formed  by  the  ascending  branches  of  the  superior 
cervical  ganglion.  E)ach  cranial  ganglion  is  connected  with 
two  cranial  nerves  or  two  branches  of  the  same  nerve,  receiving 
from  one  a  motor  and  from  the  other  a  sensitive  branch,  and  is 
also  connected  with  the  rest  of  the  sympathetic  system  by  a 
communicating  branch.  These  various  communicating  branch- 
es form  the  roots  of  the  ganglion.  The  four  cranial  ganglia 
are  the  opthalmic,  the  spheno-palatine,  the  otic  and  the 
submaxillar3^ 

Opthalmic  Ganglion,  or  Ciliary  Ganglion. 

The  opthalmic  or  lenticular  ganglion  is  found  in  the  orbit 
lying  on  the  outer  side  of  the  optic  nerve  close  to  the  optic 
foramen,  with  the  external  rectus  on  its  outer  side  and  itself 
lying  on  the  opthalmic  artery.  It  is  small  and  reddish  gray 
in  color  and  receives  three  roots,  or  branches  of  communication. 

Its  sensitive  root  is  furnished  by  the  nasal  nerve  ;  its 
motor  root  by  the  branch  of  the  third  nerve  sent  to  the  infe- 


THE  SYMPATHETIC  NERVES.  483 

rior  oblique  muscle  ;  its  synifiathetic  root  by  the  cavernous 
plexus.  The  sympathetic  root  frequently  blended  with  the 
long-  or  sensory  root. 

Its  brcniclies  of  distribiitioii^  known  as  ciliary,  five  or  six 
in  number,  pierce  the  sclerotic  coat  around  the  optic  nerve 
and  ramifying"  between  the  tunics  of  the  eyeball  terminate  in 
the  iris. 

Spheno-Palatine  Ganglion. 

The  sphe)io-palati)ie,  or  MeckeV s  gang'lion,  is  the  larg-est 
of  the  cranial  g-ang-lia  and  is  found  lying-  in  the  spheno-max- 
illary  fossa  just  beneath  the  superior  maxillary  division  of  the 
fifth  nerve,  and  close  to  the  spheno-palatine  foramen. 

Its  sensitive  roo/ consists  of  two  filaments  from  the  superior 
maxillary  nerve:  its  motor  root  is  derived  from  the  facial  nerve 
throug-h  the  Vidian  ;  its  sympathetic  root  is  from  the  carotid 
plexus.  The  last  two  roots  reach  the  g^ang-lion  tog^ether,  i.e., 
they  are  in  the  same  sheath  and  form  apparently  one  nerve  ; 
but  the  motor  root,  coming-,  from  the  Vidian,  separates  from 
the  other  branch  of  that  nerve  at  the  termination  of  the 
Vidian  canal,  the  other  branch,  the  g-reat  superficial  petrosal 
nerve,  g-oing-  to  tne  facial  throug-h  the  hiatus  Fallopii.  The 
branches  of  distribution  of  this  g-angflion  are  four,  palatine 
pharyng-eal,  superior  nasal  and  naso-palatine. 

The  three  palatine  branches,  anterior,  middle,  "ajvA posterior, 
descend  to  supply  the  roof  of  the  mouth,  soft  palate  and  ton- 
sils. The  anterior  palatine  passes  downward  throug-h  the 
posterior  palatine  canal,  emerg-es  upon  the  hard  palate  and 
runs  forward  and  inward  to  the  anterior  palatine  foramen, 
communicating-  with  the  naso-palatine  nerve.  In  the  posterior 
palatine  canal  a  branch  is  g-iven  oif  to  the  nose,  the  inferior 
nasal,  which  supplies  membrane  of  the  middle  meatus  and 
middle  and  inferior  turbinated  bones.  Just  as  it  emerges 
from  the  canal  it  gives  off  branches  to  the  soft  palate. 

The  middle  palatine,  ofteu  absent,  g-ives  branches  to  the 
tonsils,  uvula  and  solt  palate. 

The  posterior  palati)ie  passes  throug-h  an  accessory  palatine 
canal  to  supply  the  levator  palati  and  azyg-os  uvulai. 


484  DESCRIPTIVE  ANATOMY. 

The  su-perior  7iasal  are  four  or  five  branches  which  enter 
the  nose  through  the  spheno-palatine  foramen  and  are  distri- 
buted to  the  superior  meatus  of  the  nose. 

The  naso-palatine  enters  the  nose  through  the  spheno-palatine 
foramen,  runs  inward  to  the  septum  and,  after  giving-  branchesr 
to  it,  enters  the  palate  through  the  naso-palatine  canal. 

The  pharyngeal  branches,  or  -pteryg-o-palatine,  passes 
through  the  pterygo-palatine  canal  to  reach  the  pharynx  where 
it  is  distributed. 

The  Vidian,  one  of  the  communicating  branches  can  be 
traced  back  through  the  Vidian  canal  to  the  middle  lacerated 
foramen  where  it  divides  into  the  large  superficial  -petrosal, 
which  enters  the  cranium  through  the  middle  lacerated 
foramen,  passes  through  the  hiatus  and  aqueductus  Pallopii 
to  be  connected  with  the  gangliform  enlargement  of  the  facial; 
and  the  deep  petrosal,  which  enters  the  carotid  canal  to  join 
the  plexus  on  the  carotid  artery. 

Otic  Ganglion. 

The  otic,  or  Arnold's  Gang-lion,  small  and  oval-shaped, 
is  situated  on  the  inner  side  of  the  inferior  maxillary  branch 
of  the  fifth  nerve,  just  after  its  exit  through  the  foramen  ovale. 
Its  sensitive  root  comes  from  the  auriculo-temporal  branch  of 
the  inferior  maxillary;  its  motor  root  from  the  nerve  to  the 
pterygoideus  internus;  its  sympathetic  root  from  the  plexus 
on  the  middle  meningeal  artery.  Its  branches  of  distribution 
are  three,  as  follows: 

A  branch  which  passes  backward  to  the  tensor  tympani 
muscle. 

A  branch  which  passes  forward  to  the  tensor  palati  muscle. 

The  nervus  petrosus  superficialis  7ninor,  which  first  enters 
the  cranium  through  a  canal  between  the  foramen  ovale  and 
foramen  spinosum  and  passing  backward  enters  the  tympanum, 
to  join  the  tympanic  plexus,  through  a  canal  on  the  base  of 
the  petrous  bone.  It  gives  off  a  branch  (nerve  of  Longet) 
which  enters  the  hiatus  Fallopii  to  join  the  intumescentia 
gangliformis  of  the  facial  nerve. 


THE  SYMPATHETIC  NERVES.  485 

The  Submaxillary  Ganglion. 

The  submaxillary  g-ang-lioii  is  a  minute  speck  situated  near 
the  posterior  border  of  the  mylo-hyoid  muscle.  It  receives 
filaments  from  the  gustatory,  from  the  facial  through  the  chorda 
tympani  and  from  the  sympathetic  on  the  facial  artery. 

The  branches  of  distribution  are  distributed  to  Wharton's 
duct,  the  mucous  membrane  of  the  mouth  and  a  few  to  the 
submaxillary  g-land. 


486  DESCRIPTIVE  ANATOMY. 


THE  OUILET  OF  THE  PELVIS. 

The  outlet  of  the  pelvis,  which  in  the  recent  subject,  is 
closed  by  various  soft  parts,  in  the  skeleton  is  seen  to  be  sur- 
rounded by  the  following*  parts:  in  front  it  is  limited  by  the 
pubic  arch,  behind  by  the  tip  of  the  coccyx ,  on  each  side,  about 
the  centre,  by  the  tuberosity  of  the  ischium  and  running-  for- 
ward from  this  the  rami  of  the  ischium  and  pubesand  backward 
from  it  the  greater  sacro-sciatic  lig-ament  or,  in  the  recent  sub- 
ject, the  lower  border  of  the  g"luteus  maximus  muscle.  In  the 
recent  subject  the  outlet  of  the  pelvis  is  divided  into  two  por- 
tions by  a  transverse  line  passing-  between  the  anterior  edg-es 
of  the  two  tuberosities  of  the  ischia,  or,  in  other  words,  from 
the  indefinite  point  on  one  side  where  the  ramus  and  tuberosity 
of  the  ischium   meet  to  a    similar  point  on  the  opposite  side. 

The  portion  lying-  in  front  of  this  line  is  called  th.Q  perineum 
and  that  lying-  behind  it  the  ischio-rectal  region. 

Ischio-Rectal  Region. 

The  ischio-rectal  region  is  bounded  in  front  by  the  transverse 
line,  behind  by  the  apex  of  the  coccyx,  laterally  by  the  g-reat 
sacro-sciatic  lig-ament  or  the  lower  edg-e  of  the  g-luteus  maximus 
muscle  and  the  tuberosity  of  the  ischium.  It  contains  three 
parts  to  be  examined,  the  anal  orifice  with  its  sphincter  mus- 
cle and,  on  each  side  of  this,  a  subdivision  known  as  the  ischior 
rectal  fossa. 

Anus. 

The  anus  is  the  termination  of  the  rectum,  and  is  kept 
habitually  closed  by  the  tonic  contraction  of  muscles  called 
sphincters,  internal  and  external.  The  sphincter  ani  internus 
was  described  with  the  structure  of  the  rectum,  it  being-  a 
muscular  ring  around  the  gut  formed  by  an  aggregation  of  its 
circular  muscular  fibres  about  an  inch  above  the  anal  orifice. 
Surrounding  the  anal  orifice,  which  is  seen  in  the  centre  of 
the  ischio  rectal  region,  is  a  thin  elliptical  muscle  called  the 


THE  OUTLET  OF  THE  PELVIS.  487 

Sphincter  ani  externus.  It  arises  from  and  around  the  tip  of 
the  coccyx  and  passes  forward  just  beneath  and  closely  adher- 
ent to  the  skin  to  surround  the  anal  orifice,  and  be  inserted  in 
front  of  it  into  a  point  in  the  centre  of  the  perineal  line  called 
the  central  point  of  the  perineum. 

Ischio-Rectal  Fossa. 

The  ischio-rectal  fossa  is  the  triangular  or  wedge-shaped 
space  lying  beside  the  anus,  one  on  each  side.  It  is  about  two 
inches  deep,  the  base  being  at  the  surface  and  its  limits  being 
indicated  by  the  anus  within,  the  tuberosity  of  the  ischium 
without,  the  transverse  line  in  front  and  the  lower  edge  of  the 
gluteus  maximus  muscle  behind.  The  apex  is  above,  and  is 
formed  by  the  coming  together  of  two  sides  of  the  space,  the 
inner  side  being  a  muscle,  called  levator  ani,  which  is  inserted 
into  the  side  of  the  lower  part  of  the  rectum,  while  the  outer 
side  is  the  obturator  internus  muscle.  The  levator  ani  mus- 
cle is  thin  and  flat  and  has  a  most  peculiar  origin,  to  undestand 
which  some  preliminary  remarks  are  necessary.  The  trans- 
versalis  fascia,  which  lies  between  the  transversalis  abdomi- 
nis muscle  and  the  parietal  layer  of  the  peritoneum,  when  it 
reaches  the  iliac  fossa,  where  it  covers  the  iliacus  internus 
muscle,  takes  the  name  of  iliac  fascia,  which,  in  turn,  when  it 
reaches  the  brim  of  the  pelvis,  assumes  the  name  of  pelvic 
fascia,  and  this  descending  into  the  pelvis  when  it  reaches  the 
commencement  of  the  obturator  foramen,  divides  into  tw^o 
layers,  one  of  which,  the  external,  passes  over  the  inner  face 
of  the  obturator  internus,  as  the  obturator  fascia  ;  while  the 
other  passes  to  the  base  of  the  bladder  and  the  side  of  the  rec- 
tum as  the  recto-vesical  fascia.  Now  just  in  the  interval  left 
by  the  splitting  of  the  pelvic  fascia  the  levator  ani  rises,  hav- 
ing internal  to  it  the  recto-vesical  fascia  and  external,  with  a 
widening  interval  between  them,  the  obturator  fascia.  Besides 
this  origin  from  the  fascia,  it  arises  posteriorl}'^  from  the  spine 
of  the  ischium  and  anteriorly  from  the  back  of  the  pubes. 
The  ischio-rectal  region  thus  described  is  found  filled  with 
adipose  tissue,  the  absorption  of  which,  in  long-continued, 
debiliating  desease,  is  the  cause  of  the  sunken  appc.irmce 
seen  there. 


488  DESCRIPTIVE  ANATOMY. 


Perineum — In  the  Male. 

The  perineum  is  that  sub-division  of  the  outlet  of  the  pelvis 
which  lies  in  front  of  the  transverse  line.  Its  limits  are  as 
follows  :  In  front  the  public  arch,  behind  the  transverse  line, 
on  each  side  the  rami  of  the  pubes  and  ischium.  Crossing- 
along-  its  centre  from  behind  forward,  and  continued  on  to  the 
scrotum,  is  a  ridg-e  of  the  integ-ument  called  the  raphe. 

Upon  careful  dissection  the  perineum  is  found  to  be  formed 
of  the  following-  constituents  from  the  surface  upward,  viz  : 

1st.   Integument. 

2d.  Several  layers  of  superficial  fascia  which  in  no  wise 
differ  from  the  g-eneral  superficial  fascia  found  beneath  the 
integ-ument  everywhere. 

3d.  A  layer  of  fascia  called  the  superficial  permealia.sci3.,since 
it  is  peculiar  to  the  perineum,  being- attached  to  the  rami  of  the 
ischium  and  the  pubes  on  each  side,  in  front  continuous  with 
the  dartos  of  the  scrotum  and  behind  attached  to  nothing  but 
terminating  by  changing  its  name,  at  the  transverse  line  mak- 
ing a  bend  on  itself  and  running  back  toward  the  pubic  arch 
under  the  name  of  deep  perineal  fascia.  It  is  separated  from 
the  superficial  perineal  fascia  by  the  root  of  the  penis  and  the 
muscles  connected  wnth  it. 

4th.  Removing  the  superficial  perineal  fascia  there  are  ex- 
posed the  root  of  the  penis  and  its  muscles.  The  root  of  the 
penis  consists  of  the  two  crura  attached,  one  on  each  side,  to 
the  rami  of  the  pubes  and  ischium,  and  of  the  bulb  of  the 
corpus  spongiosm,  which  lies  between  these. 

The  muscles  which  are  exposed  are  three  pairs — 

Transversus  f>erinei,,  which  arises  on  each  side  from  the 
spot  w^here  the  ramus  of  the  ischium  is  continued  into  the 
tuberosity,  and  passes  transversely  inward  to  meet  its  fello^v 
in  the  centre.  The  point  where  the  two  perinei  are  inserted 
into  each  other  is  called  the  perineal  centre.  It  should  be 
observed  that  the  course  of  these  muscles  corresponds  with 
the  transverse  line. 

Accelerator  iirincE,  This  muscle  arises  from  the  perineal 
centre  and  from  the  raphe   between  it  and  its  fellow.     The 


THE  OUTLET  OF  THE  PELVIS.  489 

greater  portion  of  its  fibres  surround  the  corpus  spong-iosutn 
to  meet  the  opposing-  muscle  on  the  top  of  the  corpus,  but  some 
of  the  fibres,  posteriorly,  are  inserted  into  the  deep  perineal 
fascia  and  ramus  of  the  pubes,  while  some  in  front  are  lost 
~in:^-ihe  corpus  cavernosum.  Its  chief  action  is  to  drive  the 
urine  forward  by  contracting  on  the  corpus  spong-iosum,  in 
which  is  the  urethra. 

Erector  Poiis  arises  from  the  rami  of  the  ischium  and  pubes, 
and  passings  forward  is  lost  on  the  upper  aspect  of  the  corpus 
cavernosum. 

After  removing:  these  muscles  and  the  root  of  the  penis  the 
deep  perineal  fascia  is  displayed.  This,  as  stated,  is  contin- 
uous at  tne  transverse  line  with  the  superficial  perineal  fascia, 
the  line  of  reflection  being-  around  the  posterior  aspect  of  the 
transverse  perineal  m  uscles.  From  this  point  it  passes  forward 
to  the  arch  of  the  pubes,  attached  on  either  side  to  the  rami  of 
the  ischium  and  pubes.  Just  below  the  arch  of  the  pubes  it 
presents  a  small,  round  opening-  for  the  passage  of  the  urethra. 
When  the  deep  perineal  fascia  is  dissected  it  is  found  to  consist 
of  two  layers,  called  the  superficial  and  deep  layers  of  the  deep 
perineal  fascia,  which  is  sometimes  called  the  triang-ular  liga- 
ment of  the  pubes.  Between  the  two  layers  are  found  blood 
vessels  and  nerves  and  a  pair  of  muscles  called  compressors 
urethras.  The  compressor  urethras  arises  from  the  point  of 
union  between  the  rami  of  the  pubes  and  ischium  and  running 
transversely  inward  divides  into  two  fasciculi,  which  meet 
those  of  the  opposite  side  and  surround  the  urethra. 


490  DESCRIPTIVE  ANATOMY. 


ORGANS  OF  GENERATION  IN  THE  FEMALE. 

The  org-ans  of  generation  in  the  female  are  divided  into 
those  within  and  those  external  to  the  pelvic  cavity.  The  ex- 
ternal organs,  vulva  clito7'is,  &c.,  occupy  the  perineal  space. 
The  boundaries  of  the  outlet  of  the  pelvis  are  the  same  in  both 
male  and  female  subjects,  but  the  ischio-rectal  region  is  wider 
and  longer  in  the  female.  In  the  mid-line  are  seen  the  open- 
ing of  the  vagina  and  the  anus  separated  by  a  mass  of  tissue 
about  one  inch  thick  called  the  perineal  body.  The  external 
organs  consist  of  Hvo  labia  viajora  surrounding  the  aperture 
of  the  vagina,  composed  externally  of  skin,  which  is  covered 
with  hairs  and  internally  of  mucous  membrane,  and  united 
both  in  front  and  behind.  Internal  to  these  are  two  thinner 
projecting  folds,  one  on  eich  side,  called  labia  minora ■> 
which  enclose  in  front  a  projecting  body,  the  clitoris.  Be- 
tween the  clitoris  and  the  mouth  of  the  vagina  is  a  space 
about  one  inch  long  called  the  vestibule,  at  the  hinder  part  of 
which,  near  the  mouth  of  the  vagina,  is  an  opening,  the 
meatus  urinarius . 

The  pelvic  organs  consist  of  an  o.^^  producing  body — the 
ovary — and  a  channel  to  convey  the  ^^^  to  the  exterior.  This 
channel  is  modified  to  perform  the  function  of  hatching — the 
uterus — and  that  of  copulation — the  vagijia. 

The  ute7'us  consists  of  an  upper  part  or  fundus,  a  middle 
portion  or  body,  and  a  lower  part  or  neck.  The  vag-ina  is  a 
short,  bent  canal  which  serves  the  double  function  of  convey- 
ing the  seamen  to  the  uterus  and  of  conducting  the  foetus  to 
the  external  world.  The  relations  which  the  uterus  and  its 
so-called  appendages  bear  to  neighboring  structures  consti- 
tutes the  remainder  of  the  study  of  the  female  generative 
organs. 

The  peritoneum  passes  over  the  brim  of  the  pelvis,  envelop- 
ing the  first  portion  of  the  rectum  completely,  and  covering 
the  upper  one  inch  of  the  second   portion   in  front,   as  in  the 


ORGANS  OF  GENERATION  IN  THE  FEMALE.  491 

male.  From  the  front  of  the  rectum  it  passes  to  the  posterior 
wall  of  the  vag^ina,  which  it  covers  for  its  upper  one  inch  or 
inch  and  a  half  ;  passes  to  the  back  of  the  uterus  and  mounts 
upon  it  to  its  top,  where  it  spreads  out  upon  either  side  to 
envelop  the  appendag-es  of  the  uterus  ;  descends  upon  the 
front  of  the  uterus,  covering-  all  of  the  front  except  that  part 
contained  within  the  vag"ina,  and  thence  passes  to  the  bladder, 
which  is  covered,  as  in  the  male,  for  its  posterior  half,  the 
peritoneum  leaping-  from  the  top  of  the  bladder  to  the  posterior 
surface  of  the  anterior  abdominal  wall,  forming  the  false  lig^a- 
ments  of  the  bladder  as  in  the  male.  That  fold  of  peritoneum 
which  extends  transversely  outward  from  the  top  of  the  uterus, 
envelops  the  appendag^esof  that  org-an  in  a  double-layered  fold 
which  forms  a  vertical  septum  extending-  transversely  across 
the  pelvic  cavity,  striking  the  lateral  pelvic  walls  a  little  be- 
hind their  middle,  is  known  as  the  broad  ligament  of  the 
uterus.  The  folds  of  peritoneum  between  the  uterus  and 
vagina  and  rectum  posteriorly  and  the  uterus  and  bladder 
anteriorly  are  known  as  the  posterior  and  anterior  ligaments 
of  the  uterus  respectively,  divided  by  the  mid-line  into  two 
anterior  and  two  posterior.  Another  lig-ament,  a  round  cord, 
extends,  in  the  folds  of  the  broad  ligament,  from  the  lateral 
aspect  of  the  uterus  to  the  internal  abdominal  ring-,  to  follow 
the  ing-uinal  canal  and  be  finally  lost  in  the  labium  majus, 
under  the  name  of  the  round  lig*ament.  The  depression  be- 
tween the  vag-ina  and  the  uterus  in  front  and  the  rectum  be- 
hind is  known  as  the  pouch  of  Douglas,  the  posterior  lig-aments 
bounding-  it  on  either  side. 

The  broad  lig-ament  encloses  between  its  folds  the  fallopian 
tube,  lig-ament  of  the  ovary,  round  lig-ament  and  ovary.  The 
fallopian  tubes  occupy  the  higfhestpart  of  the  broad  lig-ament, 
extending-  outward  from  the  upper  ang-le  of  the  uterus  to  become 
closely  connected  with  the  ovary.  They  enlarg-e  as  they  pass 
outward  and  form  at  the  extremity  a  trumpet-shaped  mouth, 
fring-ed  by  diverging-  processes  or  fimbriae,  one  of  which  is 
attached  to  the  ovary.  The  tube  is  tortuous  through  the  greater 
part  of  its  course  and  when  stretched  out  is  about  five  inches 
long-,     A  little  behind  and  below   the  fallopian  tube  is  a  small 


492  DESCRIPTIVE  ANATOMY. 

round  cord,  the  lig-ament  of  the  ovary,  which  attaches  the 
ovary  to  the  upper  part  of  the  side  of  the  uterus. 

The  ovary  is  about  one  and  a  half  inches  long,  one  inch  v^ude 
and  half  an  inch  thick.  One  end  looks  toward  the  uterus,  one 
end  outward,  one  surface  upward  and  forward,  the  other 
downward  and  backward.  It  is  completely  invested  by  peri- 
toneum, bulg-ing-  the  posterior  folds  of  the  broad  lig-ament  and 
appearing"  not  to  be  in  contact  with  the  anterior  fold.  It  is 
held  to  the  uterus  by  its  lig-aments  and  the  ova  formed  by  it 
are  conducted  to  the  uterus  by  the  fallopian  tube. 

The  lower  end  of  the  uterus  projects  into  the  vag-ina,  which 
thus  surrounds  the  neck  of  the  uterus,  cutting-  off  the  lower 
portion  of  that  org-an  from  relation  with  surrounding-  viscera. 
The  vag-ina  extends  hig-her  up  on  the  uterus  posteriorly  than 
anteriorly. 

The  rectum  is  about  the  same  leng-th  as  in  the  male,  and  is 
divided  into  three  portions  for  study.  Its  lateral  and  posterior 
relations  are  the  same  as  in  the  male,  while  the  anterior  rela- 
tions are  different.  The  first  part  of  the  rectum  has  in  front 
of  it  the  uterus,  separated  from  it  by  convolutions  of  the  small 
intestine.  The  upper  inch  of  the  second  portion,  that  part 
covered  by  peritoneum  in  front,  is  separated,  by  convolu- 
tions of  the  small  intestine,  from  the  posterior  wall  of  the 
vag-ina,  which  in  turn  cuts  off  the  neck  of  the  uterus.  The 
remainder  of  the  second  portion  is  adherent  to  the  posterior 
wall  of  the  vagina.  The  third  part  of  the  rectum  passes 
downward  and  backward,  diverging-  from  the  vagina,  the 
interval  between  the  two  being  filled  by  a  triangular  mass 
of  connective  tissue  forming  the  perineal  body  and  corres- 
ponding to  the  tissue  between  the  bulb  of  the  corpus  spongiosum 
and  the  rectum  in  the  male.  The  ureter  bears  the  same  relation 
to  the  rectum  as  in  the  male,  and  lies  upon  the  side  of  the  vagina, 
which  cuts  it  off  from  relation  with  the  neck  of  the  uterus. 

The.  female  bladder  occupies  the  same  position  as  in  the  male, 
lying  behind  the  symphysis  pubis  and  bearing  the  same  rela- 
tion to  the  peritoneum.  The  anterior  and  lateral  relations  are 
also  the  same,  except  that  there  is  no  vas  deferens,  the  position 


ORGANS  OF  GENERATION  IN  THE  FEMALE.  493 

of  this  structure  being  in  part  occupied  by  the  round  lig-ament, 
which  lies  above  and  internal  to  the  external  iliac  artery.  The 
posterior  surface  of  the  bladder  is  separated  from  the  anterior 
wall  of  the  uterus  bv  some  convolutions  of  the  small  intestine. 
The  base  of  the  bladder  looks  more  nearl}^  downward  than  in 
the  male  and  rests  for  its  anterior  three-fourths  upon  the  an- 
terior wall  of  the  vagina,  to  which  it  is  firmly  adherent,  its 
posterior  one-fourth  being  covered  by  peritoneum.  The 
urethra  is  nearly  straight,  but  has  a  slight  upward  concavity. 
It  lies  on  the  anterior  wall  of  the  vagina,  is  about  two  inches 
long,  runs  through  an  opening  in  the  triangular  ligament 
about  one  inch  below  the  symphsis  pubis,  is  surrounded  by 
muscular  fibres  forming  what  is  called  the  compressor  urethrae, 
and  terminates  in  the  vestibule  at  the  meatus  urinarius. 

The  vagina  is  the  canal  of  communication  between  the 
uterus  and  the  vulva.  It  is  directed  obliquely  downward  and 
forward,  corresponding  to  the  axis  of  the  outlet  of  the  pelvis, 
while  the  uterus  corresponds  to  the  axis  of  the  brim,  the  two 
thus  forming  a  curve  whose  concavity  is  forward.  It  is  com- 
pressed, so  that  its  anterior  and  posterior  walls  are  in  contact. 
Its  anterior  wall  is  about  two  and  a  half  inches  in  length,  its 
posterior  about  three  and  a  half.  It  is  partly  closed  in  the 
virgin  by  the  hymen.  The  relations  of  the  vagina  have  been 
given  in  connection  with  other  structures. 


494  DESCRIPTIVE  ANATOMY. 


Inguinal  hernia  is  the  protrusion  of  some  portion  of  the 
abdominal  contents  through  the  abdominal  wall,  making  its 
way  along  the  inguinal  canal.  The  parts  concerned  are  the 
lower  fibres  of  the  broad  muscles  of  the  abdomen,  their  super- 
ficial and  deep  coverings,  and  the  structures  composing  the 
scrotum. 

There  is  no  deep  fascia  investing  the  broad  muscles  of  the 
abdomen.  When  the  integument  is  removed,  two  layers  of 
superficial  fascia  are  seen,  separated  from  each  other  by  the 
superficial  blood  vessels  and  nerves,  the  deeper  of  the  two 
being  the  stronger.  The  removal  of  the  deep  layer  exposes 
the  lower  portion  of  the  aponeurosis  of  the  external  oblique 
muscle,  known  as  Poupart's  ligament,  which  extends  from  the 
anterior  superior  spinous  process  of  the  ilium  to  the  spine  of 
the  pubes,  the  inner  portion  forming  the  outer,  or  lower,  pillar 
of  the  external,  or  suferflciaU  abdomijial  ring.  Poupart's 
ligament  is  folded  upon  itself,  backward  and  upward,  forming 
a  groove  directed  upward  and  inward.  To  its  posterior  face 
is  attached  the  transversalis  fascia,  where  it  becomes  continu- 
ous with  the  iliac,  while  its  anterior  face  is  continuous  with 
the  fascia  lata  and  has  adherent  to  it  the  deep  layer  of  the 
superficial  fascia.  Before  reaching  the  spine  of  the  pubes, 
Poupart's  ligament  sends  downward  and  backward  a  mass  of 
fibres,  with  its  base  outward  and  apex  inward,  to  be  attached 
to  the  spine  and  pectineal  line  of  the  pubes,  under  the  name  of 
Gimbernat's  ligament.  Turning  down  Poupart's  ligament  we 
expose  the  combined  origin  of  the  internal  oblique  and  trans- 
versalis muscles,  which  arches  upward  and  inward,  muscular, 
to  form  the  conjoined  arch,  becomes  tendinous  and  arches 
downward  and  inward  as  the  conjoined  tendon,  which  is  in- 
serted into  the  crest  and  pectineal  line  of  the  pubes  behind  the 
superficial  abdominal  ring.  The  outer  abutment  of  this  arch 
is  at  the  middle  of  Poupart's  ligament,  the  inner  one-half  inch 


INGUINAL  HERNIA.  495 

external  to  the  spine  of  the  pubes,  while  the  centre  of  the  arch 
is  one-half  inch  above  Poupart's  lig-ament.  Cutting-  away 
these  structures  we  come  to  the  transversalis  fascia,  behind 
which  is  the  parietal  layer  of  the  peritoneum,  the  two  being- 
separated  by  some  loose  connective  tissue  and  fat.  In  the 
transversalis  fascia  is  a  second  opening-,  called  the  deep  or  in- 
ternal abdominal  ri)ig:  At  the  lower,  inner,  part  of  the 
aponeurosis  of  the  external  oblique  muscle  there  is  atriang-ular 
opening-,  caused  by  the  diverg-ence  of  the  fibres  of  the  aponeu- 
rosis, known  as  the  superficial  or  external  abdominal  ring-;  the 
apex  of  the  opening-  being-  directed  upward  and  outward,  its 
base  downward  and  inward  and  corresponding-  to  the  crest  of 
the  pubes.  The  lateral  boundaries  of  this  ring-  are  known  as 
its  pillars — internal,  or  superior,  attached  to  the  front  of  the 
symphsis  pubis,  external,  or  inferior,  attached  to  the  spine  of 
the  pubes.  The  latter  is  simply  the  inner  portion  of  Poupart's 
lig-ament.  Around  the  marg-ins  of  this  ring-  the  deep  layer  of 
the  superficial  fascia  is  attached,  forming-  what  is  called  the 
inter-columnar  fascia.  The  two  layers  become  continuous 
below  with  the  dartos  of  the  scrotum.  The  apex  of  the  trian- 
g-le  is  obscured  by  a  few  fibres  which  cross  the  others  at  rig-ht 
ang-les  and  prevent  a  further  divergence  of  the  fibres  and 
consequent  widening-  of  the  triang-le.  These  are  called  the 
inter-columnar  fibres. 

About  one  and  one-half  inches  above  and  external  to  this 
opening-,  nearly  opposite  the  centre  of  Poupart's  lig-ament, 
there  is  a  hole  in  the  transversalis  fascia  called  the  deep  or 
internal  abdominal  ring-,  situated  a  little  less  than  one-half  an 
inch  above  Poupart's  lig-ament  and  internal  to  the  outer  abut- 
ment of  the  arch.  Externally  this  ring-  is  bounded  by  the 
conjoined  arch,  internally  by  the  deep epig-astric  artery,  below 
by  Poupart's  lig-ament.  The  ring-  does  not  exist  in  a  healthy 
subject.  Throug-h  this  ring-  the  testicle  descends  in  the  foe- 
tus, and  to  its  marg-ins  is  attached  a  prolong-ation  of  the 
transversalis  fascia,  the  infundibuliform  tube  of  fascia, 
which  forms  one  of  the  coats  of  the  hernia.  Extending-  be- 
tween the  two  ring-s  there  is  a  canal,  about  one  and  one-half 
inches  long-,  the  inguinal  or  spermatic  canal,  which,  in  health, 


496  DESCRIPTIVE  ANATOMY. 

transmits  the  spermatic  cord,  in  the  male,  or  the  round  lig'a- 
ment,  in  the  female,  while,  patholog"ically,  it  transmits  the 
g-ut  in  a  hernia. 

The  sperynatic  canal  is  limited  internally  by  the  superficial 
abdominal,  externally  by  the  deep,  abdominal  ring-,  and  its 
walls  are  formed  as  follows  :  Below  by  the  g-rooved  upper 
surface  of  Poupart's  lig-ament  ;  above  by  the  conjoined  arch  ; 
in  front  by  the  aponeurosis  of  the  external  oblique  ;  behind, 
by  the  transversalis  fascia  and  parietal  layer  of  peritoneum 
throug-hout  its  extent,  while,  for  about  its  inner  half,  the 
conjoined  tendon  lies  in  front  of  those  structures.  The  canal 
contains  the  neck  of  the  infundibuliform  tube  of  fascia, 
arteries,  nerves,  lymphatics  and  the  duct  from  the  testicle. 

On  the  visceral  face  of  the  peritoneum  there  may  sometimes 
be  seen  a  dimple  which  corresponds  to  the  deep  abdominal 
ring-,  and,  internal  to  this,  a  ridg-e  which  is  formed  by  the 
deep  epig-astric  artery.  The  space  between  the  ridg-e  and 
the  mid-line  of  the  body  is  called  the  internal  inguinal  fossa, 
that  external  to  the  ridg-e  the  external  inguinal  fossa. 

The  testicles,  in  their  descent,  enter  at  the  deep  ring-,  pass 
throug-h  the  ing-uinal  canal  and  make  their  exit  at  the  super- 
ficial ring-.  The  cause  of  this  descent  is  not  accurately  known, 
but  it  is  aided  by  the  g-ubernaculum  testis,  a  mass  of  unstriated 
muscular  fibres,  attached  by  one  extremity  to  the  testicle  and 
by  the  other  to  the  marg-ins  of  the  superficial  abdominal  ring-. 
In  its  descent  the  testicle  carries  with  it  the  structures  closing" 
the  two  abdominal  ring-s.  Thus,  it  presses  upon  the  perito- 
neum at  the  deep  abdominal  ring-,  invag-inates  it  and  forces 
along-  a  process  of  this  membrane  which  becomes  the  deepest 
layer  investing-  the  testicle  and  is  known  as  the  tunica  vag-i- 
nalis;  next  it  forces  along-  a  process  of  the  transversalis  fascia, 
which,  after  the  descent  of  the  testicle,  becomes  attached  to 
the  deep  ring-  forming-  the  infundibuliform  tube  of  fascia  ; 
then,  while  passing-  beneath  the  conjoined  arch,  muscular 
fibres,  arrang-ed  in  loops  around  the  cord,  are  contributed 
forming-  the  cremaster  muscle,  which  is  attached  internally 
to  the  sheath  of  the  rectus  and  externally  to  Poupart's  lig-a- 
ment.     These  loops  are  attached  to  each  other  by  fascia  called 


INGUINAL  HERNIA.  497 

the  cremasteric  fascia.  Lastly,  the  testicle  carries  with  it  a 
process  of  the  intercolumnar  fascia,  forming-  the  external  cov- 
ering- of  the  cord,  which  is,  of  course,  covered  by  the  super- 
ficial fascia  and  integ-ument.  Shortly  after  birth  the  tunica 
vaginalis  is  obliterated  from  the  internal  ring-  to  within  a 
short  distance  of  the  testicle. 

When,  from  weakening  of  the  abdominal  wall,  or  other 
cause,  an  inguinal  hernia  is  produced,  it  usually  follows  the 
course  of  the  testicle  in  its  descent,  and,  hence,  its  coverings 
would  be  similar  to  those  of  the  testicle.  This  form  is  known 
as  an  oblique  inguincd  hernia,  subdivided  into  complete,  when 
it  escapes  from  the  superficial  abdominal  ring-,  and  incomplete, 
or  bubonocele,  when  it  remains  in  the  ing-uinal  canal.  A 
complete  inguinal  hernia  pushes  before  it  the  peritoneum 
closing  the  deep  abdominal  ring-,  which  forms  the  hernial  sac, 
enters  the  inguinal  canal,  receiving-  an  investment  from  the 
infundibulum  tube  of  fascia  and  the  cremaster  muscle,  passes 
through  the  superficial  abdominal  ring-,  carrying-  with  it  a 
covering-  furnished  by  the  intercolumnar  fascia,  descends  in 
front  of  the  cord  into  the  scrotum  and  is  invested  by  the  super- 
ficial fascia  and  the  integ-ument.  In  incomplete  hernia  the 
coverings  cease  at  the  superficial  abdominal  ring. 

When  the  peritoneal  pouch  is  not  obliterated,  there  is  a 
direct  communication  between  the  abdominal  and  scrotal  cavi- 
ties, and  the  peritoneal  covering  of  ,the  hernia  is  the  tunica 
vaginalis.  This  form  of  hernia  constitutes  what  is  known  as 
cong'enital  hernia. 

In  infantile  hernia  the  pouch  is  closed  at  the  deep  abdo- 
minal ring-  only,  and  the  gut  descends  behind  the  tunica 
vaginalis,  having-  three  peritoneal  layers  in  front,  viz:  the  two 
layers  of  the  tunica  vaginalis  and  one  layer  of  the  proper 
investing  sac  of  the  hernia. 

In  the  encysted  form  the  gut,  carrying  its  own  sac,  projects 
into  the  tunica  vaginalis,  leaving-  in  front  of  it  but  two  serous 
layers,  viz:  one  of  its  own  sac  and  one  from  the  tunica 
vaginalis. 

Des  An  at— 32 


498  DESCRIPTIVE  ANATOMY. 

Direct  Inguinae  Hernia. — Hesselbach's  triangle  is 
bounded  externally  by  the  deep  epigastric  artery,  internally 
by  the  rectus  abdominis,  below  by  Poupart's  ligament.  It 
is  crossed  by  the  conjoined  tendon  of  internal  oblique  and 
transversalis  muscles.  Hernia  m.ay  occur  either  external 
to  or  through  this  tendon.  When  the  hernia  is  external  to  the 
tendon  it  follows  a  part  of  the  inguinal  canal  and  has  the  same 
coverings  as  an  oblique  inguinal  hernia,  except  that  the  infun- 
dibuliform  tube  is  replaced  by  another  prolongation  of  the 
transversalis  fascia.  When  through  the  tendon  the  latter  is 
pushed  before  the  gut,  which  has  the  same  coverings  as  in  the 
oblique  form,  except  that  the  infundibuliform  tube  is  replaced 
by  another  portion  of  the  transversalis  fascia,  and  the  conjoined 
tendon  replaces  the  cremaster  muscle.  Occasionally  the 
hernia  may  split  the  tendon  instead  of  pushing  it  before  it. 


FEMORAL  HERNIA.  499 


FEMORAL  HERNIA. 

Definition.  —  The  protrusion  of  an  abdominal  viscus 
throug-h  the  femoral  or  crural  ring". 

Parts  Concerned. — Behind  the  femoral  arch  is  found  the 
upper  border  of  the  pubic  bone,  marked,  from  within  outward, 
b}'  the  ang-le,  crest,  spine,  pectineal  line,  triang-le  and  eminence 
and  the  psoas  g-roove.  Stretching-  from  the  anterior  superior 
spinous  process  of  the  ilium  to  the  pubic  spine  and  pectineal 
line,  is  Poupart's  ligament,  forming-  the  femoral  or  crural 
arch.  Gimbernat's  lig-ament  is  the^  portion  of  Poupart's  lig-- 
ament  which  is  inserted  into  the  pectineal  line.  The  other 
structures  concerned  are  the  iliac  artery  and  vein  and  their 
sheath,  the  peritoneum  and  fascia  closing-  the  mouth  of  the 
ring-,  the  fascia  lata,  cribriform  and  superficial  fasciae  and  the 
integument. 

The  space  between  Poupart's  lig-ament  and  the  upper  bor- 
der of  the  pubes  is  filled  from  without  inward  by  the  psoas 
and  iliacus  muscles,  the  anterior  crural  nerve  and  the  femoral 
sheath  containing  the  femoral  artery  and  vein  and  having-  in  it 
an  unoccupied  space  internal  to  the  vein.  This  sheath 
is  formed  in  front  by  the  transversalis,  behind  by  the  iliac 
fascia. 

Femoral  Ring. — ^h^  fonoral  7-ing-  is  the  upper  opening- 
of  the  femoral  canal.  Internally  it  is  bounded  by  the  outer 
edg-e  of  Gimbernat's  ligament  ;  externally  by  a  septum  in  the 
sheath  separating  the  open  space  from  the  femoral  vein  ;  above 
is  Poupart's  lig-ament  ;  below,  the  upper  border  of  the  pubes 
and  the  orig-in  of  the  pectineus  muscle.  The  femoral  canal 
extends  downward  in  the  sheath  for  about  one  inch  and  is 
lined  by  a  prolong-atiQn  of  fascia  which  covers  the  vessels  and 
is  known  as  the  fascia  propria.  The  canal  terminates  b}''  the  con- 
traction of  the  sheath  so  as  to  closely  hug-  the  vessels.  The 
femoral  ring-  is  closed  above  by  the  peritoneum  and  a  thin 
layer  of  fascia  called  septum  crurale,  or  femorale,  which  usually 
has  lying-  upon  it  a  lymphatic  g-land. 


500  DESCRIPTIVE  ANATOMY. 

Blood  Vessels. — Just  beneath  Poupart's  ligament  the 
external  iliac  vessels  terminate  by  becoming*  the  femoral;  but, 
before  its  termination,  the  external  iliac  artery  g-ives  off  a 
larg-e  branch  called  the  deep  epigastric,  which  lies  above  and  ex- 
ternal to  the  femoral  ring  and  betw^een  it  and  the  deep  abdominal 
ring.  The  external  iliac  vein  lies  to  the  outer  side  of  the  ring, 
so  that  in  all  cases  there  are  blood  vessels  above  and  external 
to  the  ring.  The  deep  epigastric  artery  sometimes  gives  off 
a  branch  called  the  obdurator,  which  may  descend  next  the 
iliac  vein  and  on  the  outer  side  of  the  ring  ;  but  it  sometimes 
passes  inward  and  downward,  arching  above  and  internal  to 
the  femoral  ring,  which  is  thus  surrounded  by  blood  vessels 
on  all  sides  except  below.  The  epigastric  also  gives  off  a 
small  pubic  branch  which  lies  above  the  ring,  but  is,  from  its 
size,  unimportant. 

Fascia  Lata. — The  investing  fascia  of  the  thigh,  or  fascia 
lata,  presents,  about  one  inch  below  Poupart's  ligament, 
an  oval  opening  called  the  saphenous  opening.  The  opening 
is  closed  in  the  recent  state.  It  runs  obliquely  downward  and 
outward,  is  about  one  inch  in  its  vertical  by  three-quarters  of 
an  inch  in  its  transverse  diameter;  its  inner  edge  is  straight 
and  prolonged  outward  behind  the  outer  edge;  its  outer  is 
curved,  runs  downward  and  outward  from  Gimbernat's  liga- 
ment to  the  inferior  cornu  and  is  called  Hey's  ligament  or  the 
falciform  process  of  Burns.  The  external  part  of  the  fascia 
is  known  as  the  iliac  portion  and  is  attached  to  the  crest  of  the 
ilium  and  the  outer  portion  of  Poupart's  ligament,  sending  in- 
ward a  spur  which  is  attached  to  the  pectineal  line,  runs  over 
the  femoral  vessels  and  forms  the  outer  boundary  of  the  saphe- 
nous opening.  The  inner  part,  called  the  pubic  portion,  is 
thin  and  weak,  is  attached  to  the  ischio-pubic  ramus  and  is 
prolonged  beneath  the  femoral  vessels.  The  saphenous  open- 
ing is  covered  by  the  skin  and  two  layers  of  superficial  fascia, 
of  which  the  deep,  under  the  name  of  cribriform  fascia,  be- 
comes adherent  to  the  margins  of  the  opening.  The  cribri- 
form fascia  is  attached  more  firmly  below  than  above,  and  hence 
tends  to  direct  a  protruding  gut  upward. 


FEMORAL  HERNIA.  501 

Course. — A  femoral  hernia  passes  downward  through  the 
femoral  ring-,  thence  down  the  canal  as  far  as  the  saphenous 
opening",  turns  forward  through  this  opening  and  then  runs 
upward  on  the  front  of  the  thigh.  The  main  causes  of  the 
ascent  are  the  firmer  attachment  of  the  cribriform  fascia  below, 
the  narrowing  of  the  femoral  canal  and  the  movements  of  the 
thigh. 

Coverings. — Femoral  hernia  pushes  before  it,  first  the 
parietal  layer  of  peritoneum  and  fat  covering  the  femoral  ring, 
then  the  septum  femorale,  fascia  propria,  cribriform  fascia, 
superficial  layer  of  the  superficial  fascia  and,  lastly,  the  skin. 


502  DESCRIPTIVE  ANATOMY. 


THE  AXILLA. 

The  space  known  by  this  name  lies  between  the  chest  wall 
internally,  the  humerus  externally  and  the  muscles  in  front 
and  behind.  In  the  skeleton  only  the  apex  of  the  space  is 
complete,  being-  bounded  in  front  by  the  clavicle,  behind  by 
the  upper  border  of  the  scapula,  internally  by  the  first  rib. 
Below  the  apex  the  space  corresponds  to  the  upper  five  ribs 
internally,  the  scapula  behind  and  the  bottom  of  the  bicipital 
groove  externally.  In  the  recent  subject  the  space  has  the 
shape  of  a  three-sided  pyramid.  The  apex  is  above,  the  base 
below  and  the  sharp  angle  external  at  the  bicipital  groove. 
The  whole  space  is  closed  in  by  soft  structures.  The  ante- 
rior wall  is  furnished  by  the  pectoralis  major,  which  covers 
the  whole  of  the  space,  while  beneath  this,  forming  only  the 
middle  of  the  anterior  wall,  is  the  pectoralis  minor.  The  pos- 
terior wall  is  formed  by  three  muscles,  subscapularis,  teres 
major  and  latissimus  dorsi;  but  the  order  in  which  they  come 
changes  in  different  parts  of  the  space.  Near  the  inner  wall  the 
order,  from  above  downward,  is  subscapularis,  teres  major, 
latissimus  dorsi;  but  near  the  external  wall,  owing  to  the  fact 
that  the  tendon  of  the  latissimus  dorsi  winds  around  the  teres 
major  and  is  inserted  above  it, the  order  is  subscapularis,  latissi- 
mus dorsi,  teres  major.  The  inner  wall  is  formed  by  the  upper 
six  serrations  of  the  serratus  magnus  muscle  and  the  intercos- 
tal muscles  corresponding  to  the  upper  five  intercostal  spaces. 
The  lower  border  of  the  muscles  which  enter  into  the  anterior 
and  posterior  boundaries  of  the  axilla  form  the  anterior  and 
posterior  axillary  folds,  of  which  the  posterior  is  the  thicker 
and  more  prominent.  Stretching  across  from  one  fold  to  the 
other,  and  continuous  with  the  investing  fascia  of  the  arm,  is 
a  strong  fascia  which  forms  the  floor  of  the  space.  The  con- 
tents of  this  space  are  the  brachial  plexus  of  nerves  and  its 
terminal  branches,  the  axillary  artery  and  vein  and  their 
branches,  lymphatic  glands  and  a  quantity  of  areolar  tissue 
and  fat. 


THE  ORGAN  OF  HEARING.  503 


THE  ORGAN  OF  HEARING. 

The  org-an  of  hearing-  is  connected  with  the  temporal  bone 
of  each  side,  and  properl}^  speaking-,  consists  of  two  organs, 
one  to  each  side.  In  the  prepared  bone  a  portion  is  still  pre- 
served, for  upon  the  base  of  the  petrous  portion  of  the  tempo- 
ral bone  the  bony  portion  of  the  external  auditory  meatus  is 
seen  ;  and  on  the  posterior  surface  of  the  petrous  portion  the 
internal  auditory  meatus,  at  the  bottom  of  which  is  seen  the 
internal  wall  of  the  inner  chamber  perforated  by  numerous 
apertures.  The  external  wall  of  the  inner  chamber  is  seen 
by  looking  into  the  external  auditory  meatus.  On  the  anterior 
face  of  the  petrous  portion  are  seen  the  bulge  of  the  superior 
semicircular  canal  and  just  external  to  this  a  depression  corre- 
sponding- to  the  roof  of  the  middle  chamber,  or  tympanum, 
the  floor  of  which  is  the  jug-ular  fossa,  on  the  basilar  face  of 
the  petrous  portion  of  the  temporal. 

The  org-an  of  hearing  is  described  as  consisting-  of  three 
portions,  or  chambers,  lying-  the  one  internal  to  the  other, 
upon  the  base  and  in  the  substance  of  the  petrous  portion  of 
the  temporal  bone.  These  three  chambers  are  known  from 
without  inward  as — 1st,  external  ear  consisting  of  three  por- 
tions, (<^)/>/;^««,  or  auricle',  {b)  meatus  auditorius  externus  \ 
{c)  nienibrana  tynipani;  2nd.,  middle  ear  or  tympanum  ;  3rd, 
internal  ear,  or  labyrinth. 

The  External  Ear. 

The  external  ear  consists  of  three  portions  named  above. 
Its  function  is  to  connect  the  sonorous  vibrations  and  convey 
them  to  the  middle  ear,  which  in  turn  transmits  them  to  the 
internal  ear,  where  they  encounter  the  sentient  nerve  of  hear- 
ing. 

The  -piwia,  or  auricle  is  the  expanded  outer  extremity  of  the 
external  chamber  found  on  the  base  of  the  petrous  portion  of 
the  temporal  bone,  contracting-  to  its  termination  in  the  exter- 


504  DESCRIPTIVE  ANATOMY. 

nal  auditory  meatus.  It  presents  a  very  uneven  surface  and 
the  various  elevations  and  depressions  have  received  individual 
names.  The  central  concavity,  leading-  to  the  external  audi- 
tory meatus,  is  called  the  concha  ;  the  more  or  less  folded 
marg-in,  or  rim,  the  helix  ;  the  pendant,  lower,  softer  portion, 
the  lobulus  ;  the  triang-ular  prominence  jutting-  out  in  front 
of  the  concha,  the  trag-us  ;  behind  and  somewhat  below  this, 
separated  from  it  by  a  notch,  is  another  projection,  the  anti- 
trag"us  ;  the  curved  elevation  between  the  helix  and  the  concha, 
or  rather  behind  the  concha,  is  the  anti-helix,  which  divides 
superiorly  enclosing*  a  depression  called  the  fossa  ovalis  ;  the 
deeply  sunken  surface  between  the  helix  and  the  anti-helix  is 
the  fossa  scaphoidea,  or  innominata. 

Tho,  pimia  varies  g-reatly  in  different^  people,  and  this  is 
especially  true  of  the  lobule.  In  structure  it  consists  of  a 
plate  of  fibro-cartilage,  whose  folds  produce  the  depressions 
and  elevations  mentioned.  This  cartilag-e  is  covered  by  integu- 
ment and  alveolar  tissue,  supporting*  various  insignificant 
muscles,  intrinsic,  intended  to  vary  its  shape,  and  giving 
attachment  to  other  small  muscles,  extrinsic,  intended  to  move 
the  pinna.  Of  the  latter  some  few  people  have  use,  but  the 
former  never  act  to  produce  visible  effect.  The  cartilag*e  is 
not  continuous  throug-hout  the  auricle,  for  it  is  altog^ether 
wanting-  in  the  lobule  and,  besides,  presents  several  fissures 
which  have  received  names.  The  pinna  is  held  in  position  by 
the  integ-ument.  by  the  extrinsic  muscles  mentioned  above  and 
by  two  lig-aments,  anterior  and  posterior.  The  anterior 
extends  from  the  helix  to  the  zygoma;  the  posterior,  from  the 
concha  to  the  mastoid  process.  Besides  these  there  are  several 
small  ligaments  passing-  from  one  part  of  the  cartilag-e  to 
another,  the  larg-est  of  which  is  that  between  the  trag-us 
and  helix. 

The  external  auditory  ineatus  is  the  canal  which  extends 
from  the  concha  to  the  tympanum,  from  which  it  is  separated 
by  the  tympanic  membrane.  It  is  rather  more  than  an  inch  in 
length,  its  direction  being  inward  and  slig-htly  forward  and 
its  course  somewhat  curved,  with  its  convexity  upward.  It  is 
smaller  in  the  centre  than  at  either  end.     It  consists  of  an 


THE  ORGAN  OF  HEARING.  505 

external  cartilag-inous  portion,  taking-  up  one-third  of  its  lengfth, 
and  an  internal,  osseous  portion,  taking"  the  remaining-  two- 
thirds.  The  osseous  portion  terminates  internally  at  an  oblique 
g-roove  for  the  attachment  of  the  membrana  tympani.  This 
portion  can  be  seen  in  the  dried  bone,  althoug-h  the  septum  in 
the  botton  is  of  course  absent.  The  outer  extremity  is  roug-h 
and  prominent  for  the  attachment  of  the  cartilag-inous  portion. 
It  is  lined  throug-hout  by  the  integ-ument  which,  toward  the 
exterior,  is  studded  with  hairs  and  contains  g-lands  for  the 
secretion  of  the  ear  wax.  The  hairs  and  wax  are  intended  to 
obstruct  the  entrance  of  insects,  &c. 

The  niembrcuia  tympani  is  the  septum  separating-  the  exter- 
nal from  the  middle  chamber,  being-  situated  at  the  inner 
extremity  of  the  external  auditory  meatus,  attached  to  the  ob- 
lique g-roove  there  found.  It  is  frag-ile,  semi-transparent, 
nearly  round,  oblique  in  its  direction  from  above  downward 
and  inward,  striking-  the  floor  at  an  ang-le  of  45°,  and  is  seen 
to  bulg-e  toward  the  tympanum,  having-  a  corresponding*  con- 
cavity externally.  Its  frame  work  is  fibro-elastic,  consisting- 
of  radiating-  and  concentric  jQbres,  the  latter  especially  seen 
near  its  circumference;  it  is  covered  externally  by  the  integ-u- 
ments  lining-  the  externally  auditory  meatus,  which  is  exceed- 
ing-ly  sensitive.  Internally  it  is  coated  by  mucous  membrane 
of  the  typanum. 

The  Middle  Ear. 

The  middle  ear,  chamber,  or  tympaimm,  lies  in  the  petrous 
portion  of  the  temporal  bone,  separated,  externally,  from  the 
meatus  auditorius  externus  by  the  membrana  tympani  ;  and 
separated,  internally,  from  the  inner  chamber,  or  labyrinth  by 
a  bony  wall  and  its  roof  corresponds  to  the  depression  on  the 
anterior  face  of  the  petrous  bone,  its  floor  to  the  jug-ular  fossa 
on  the  basilar  face  of  that  bone.  Its  anterior  wall  is  a  bony 
partition  interposed  between  it  and  the  internal  carotid  artery 
and  its  posterior  wall  is  the  cellular  substance  of  the  mastoid 
portion  of  the  temporal  bone.  Owing-  to  the  obliquity  of  the 
inner  and  outer  walls,  the  tympanum  is  much  narrower  trans- 
versely, below  than  above.     The  leng-th  of  its  roof  from  with- 


506  DESCRIPTIVE  ANATOMY. 

out  inward  is  about  three  lines,  the  floor  being-  scarcely  more 
than  one  line.  It  presents  for  examination  six  walls,  two  of 
which — floor  and  roof — have  nothing-  noteworthy.  The  outer 
wall  has  been  described  as  the  membrana  tympani,  having- 
attached  to  it  a  chain  of  bones,  which  extends  to  the  inner 
wall. 

The  internal  wall  is  the  bony  partition  between  the  tympa- 
num and  the  labyrinth,  upon  which  are  seen  the  following' 
appearances  :  {a)  a  ridg-e  at  its  upper  part  corresponding-  to 
the  acqueduct  of  Fallopius  ;  {b)  just  beneath  this  a  kidney- 
shaped  aperture,  opening-  into  one  of  the  apartments  of  the 
labyrinth,  called  the  fenestra  ovalis.  This  is  closed  during- 
life  by  a  membrane  to  which  is  attached  the  foot  of  the  stapes  ; 
(6')  below  this  is  a  bulg-ing-  surface  known  as  the  promontory  ; 
{d)  beneath  this  is  a  second  opening-  oval,  or  triang-ular  in 
shape,  called  the  fenestra  rotunda,  which  is  likewise  closed  by 
a  membrane  and  establishes  communication  with  another  part 
of  the  labyrinth  called  the  cochlea. 

The  posterior  wall  presents  several  small  opening's  into  the 
mastoid  cells  and  the  opening-  for  the  entrance  of  the  chorda 
tympani,  iter  chordae  posterius,  which  crosses  the  tympanum 
to  g-ain  exit  on  its  anterior  wall.  There  is  also  a  conical  pro- 
jection, the  pyramid,  which  has  at  its  summit  an  opening-  for 
the  stapedius  muscle. 

On  the  anterior  wall  are  seen  :  {a)  the  fissure  of  Glaser  ; 
{b)  the  opening-  of  exit  of  the  chorda  tympani,  iter  chordae  an- 
terius,  or  canal  of  Hug-uier  ;  {c)  two  small  opening-s,  separated 
by  a  thin  plate  of  bone,  the  upper  called  the  opening-  for  the 
tensor  tympani.  the  lower  the  opening-  for  the  Eustachian  tube, 
and  the  dividing  septum  the  cochleariform  process.  Stretch- 
ing- across  the  tympanum  from  the  membrana  tympani,  extern- 
ally, to  the  fenestra  ovalis  internally  are  seen  three  smiU 
bones,  malleus,  incus  and  stapes.  The  malleus  is  the  outer- 
most of  the  three,  resting-  ag-ainst  the  membrana  tympani  ex- 
ternally and  articulating-  with  the  incus  internally.  It  consists 
of  a  head,  for  articulation  with  the  incus,  a  neck  and  three 
processes.  One  of  the  processes  is  called  the  handle,  manu- 
brium, and  lies  embedded  in  the  membrana  tympani,  half  way 


THE  ORGAN  OF  HEARING.  507 

to  the  floor  from  above  downward.  Another,  the  long-  process, 
processus  g-racilis,  passes  downward  to  the  fissure  of  Glaser  ; 
while  the  third,  the  short  process,  bulges  outward  from  the 
neck.  The  incus  is  so  called  from  its  resemblance  to  an  anvil. 
It  consists  of  a  body,  for  articulation  with  the  head  of  the 
malleus,  and  two  processes.  The  short  process  passes  back- 
ward to  the  opening"  of  the  mastoid  cells  in  the  posterior  wall; 
the  long",  passes  downward  to  articulate  with  the  head  of  the 
stapes,  terminating-  in  an  enlarg-ement,  called  the  os  orbiculare. 
The  stapes,  stirrup,  projects  inward  from  the  os  orbiculare, 
with  which  it  articulates  by  a  head.  Succeeding-  the  head 
comes  the  neck  and  diverging  from  this  are  the  two  crura, 
one  to  either  side,  which  are  connected  at  their  distal  extrem- 
ity by  a  plate,  called  the  foot,  which  is  exactly  fitted  into  the 
fenestra  ovalis.  When  the  child  is  born  those  bones  have  at- 
tained nearly  their  full  size.  They  are  held  tog-ether  by  lig-a- 
ments  and  g-ive  attachment  to  several  small  muscles  which  are 
intended  to  move  the  bones  on  one  another  and  thus  relax,  or 
tig-hten  the  membrana  tympani,  or  the  membrane  of  the 
fenestra  ovalis.  This  latter  membrane  is  in  fact  composed  of 
two  layers,  and  the  fenestra  ovalis  is  closed  successively  by 
the  following-  parts  from  without  inward,  viz  :  1st,  the  mucous 
membrane  of  the  tympanum  ;  2d,  beneath  this  the  foot  of  the 
stirrup  ;  3d,  on  the  labyrinthine  surface  this  foot  is  coated  by 
the  serous  membrane  lining-  the  labyrinth.  The  arrang-ement 
for  closing-  the  fenestra  rotunda  is  similar  in  consisting-  of  three 
elements  :  (1st),  a  fibrous  membrane  coated  by  (2d)  the  mucous 
membrane  of  the  tympanum  externally  and  (3d)  internally  by 
the  serous  membrane  of  the  labyrinth.  It  is  constructed  so 
much  like  the  membrana  tympani  that  it  has  been  called  the 
membrana  tympani  secundaria.  The  ossiculaauditus  are  held 
to  one  another  and  in  position  by  means  of  small  lig-aments. 
The  head  of- the  malleus  is  held  to  the  body  of  the  incus  by  a 
capsular  ligament  ;  and  another  capsular  lig-ament  binds  to- 
gether the  os  orbicularis  and  the  head  of  the  stapes.  The 
lig-aments  holding- the  bones  tog-ether  are  three  in  nnmber:  1st, 
the  foot  of  the  stapes  is  held  to  the  fenestra  ovalis  by  means  of 
lig-amentous  fibres  ;   2d,  there  is  a  suspensory  lig-ament  of  the 


508  DESCRIPTIVE  ANATOMY. 

malleus  consisting-  of  a  few  lig'amentous. fibres  passing-  be- 
tween its  head  and  the  roof  of  the  tympanum  ;  3d,  a  band  of 
fibres  attaches  the  short  process  of  the  incus  to  the  opening-  of 
the  mastoid  cells.  These  bones,  thus  permitted  motion  by 
means  of  the  lig-aments,  are  moved  not  only  by  the  vibrations  of 
the  membrana  tympani  but  by  two  small  muscles,  viz  :  The 
tensor  tympani  which  spring's  from  the  apex  of  the  basilar 
surface  of  the  petrous  bone  and  the  upper  aspect  of  the  carti- 
laginous portion  of  the  E^ustachian  tube  and  enters  the  open- 
ing- in  the  tympanum  known  by  its  name,  and  found  just  above 
the  processus  cochleariformis,  which  separates  it  from  the 
opening-  of  the  E^ustachian  tube ;  it  also  derives  a  few  fibres 
from  the  canal  it  traverses.  When  it  reaches  the  anterior 
wall  of  the  typanum  its  tendon  turns  outward  and  is  inserted 
into  the  malleus  at  the  junction  of  the  manubrium  and  long- 
process  of  the  malleus.  The  stapedius  is  far  the  smallest  mus- 
cle in  the  body.  It  arises  within  the  hollow  pyramid,  on  the 
posterior  wall  of  the  tympanum,  emerg-es  from  the  opening- 
on  the  summit  of  the  pyramid  and  is  inserted  by  a  tendon  into 
the  neck  of  the  stapes.  The  action  of  the  stapedius  is  to  reg-- 
ulate  the  pressure  of  the  foot  of  the  stapes  ag-ainst  the 
fenestra  ovalis. 

The  Eustachian  Tube. 

The  Eustachian  tube  is  a  canal,  which  establishes  communi- 
cation between  the  air  in  the  tympanum  and  the  outside 
atmosphere.  It  passes  from  the  anterior  wall  of  the  tympanum, 
where  its  opening-  is  seen  just  beneath  the  processus  cochlear- 
iformis, downward,  forward  and  inward,  to  terminate  in  the 
phar3mx,  just  behind  the  opening-  of  the  posterior  nares.  Its 
lower  third  is  cartilag-inous;   its  upper  two-thirds  osseous. 

The  Internal  Ear. 

The  internal  ear,  or  labyrinth  is  the  innermost  of  the  three 
chambers,  which  constitute  the  org-an  of  hearing-  and  is  intended 
for  the  terminal  ramifications  of  the  auditory  nerve,  which 
reaches  it  throug-h  the  internal  auditory  meatus,  on  the  centre 
of  the  posterior  face  of  the  petrous  bone,  and  for  the  reception 
of  the  communicated  vibrations  of  air,  which  reach  it  throug-h 


THE  ORGAN  OF  HEARING.  509 

the  tympanum.  It  consists  of  an  osseous  and  a  membranous 
lab3'rinth,  the  osseous  being-  divided  into  three  chambers, 
which,  however,  communicate  with  one  another.  These  three 
parts  are  placed  one  behind  the  other:  the  anterior  is  called  the 
cochlea,  the  middle  the  vestibule,  the  posterior  the  three 
semicircular  canals.     They  are  all  lined  by  a  serous  coat. 

The  Vestibule. 

The  Vestibule  is  a  three  cornered  cavity,  having-  communi- 
cation with  the  tympanum  throug-h  the  fenestra  ovalis.  Kach 
corner  is  called  a  ventricle  and  the  three  are  known  as  anterior, 
superior  and  posterior.  In  the  anterior  are  seen  the  following" 
objects:  1st,  a  depression,  called  fovea  hemispherica;  2d,  a 
number  of  minute  apertures,  called  the  macula  cribrosa;  3d,  a 
ridge,  the  eminentia  pyramidalis;  4th,  the  opening-  into  the 
cochlea,  scala  vestibule.  In  the  superior  we  have:  1st,  a 
depression — the  fovea  hemi-elliptica;  2nd,  the  two  openings 
of  semicircular  canals — the  dilated  extremities  of  the  superior 
and  horizontal.  The  posterior  presents:  1st,  a  depression — 
fovea  sulciformis;  2d,  the  opening  of  the  aqueduct  of  the  ves- 
tibule; 3d,  the  dilated  extremity  of  the  oblique  semicircular 
canal,  the  common  aperture  for  this  canal  and  the  superior  and 
the  opening  of  the  horizontal  canal. 

The  Semicircular  Canals. 

These  canals  are  channels  hollowed  in  the  petrous  portion 
of  the  temporal  bone.  They  are  three  in  number,  each  about 
one-twentieth  of  an  inch  in  diameter,  and  placed  at  right 
angles  to  one  another.  Kach  forms  rather  more  than  a  semi- 
circle and  presents  near  one  extremity  an  enlargement,  called 
the  ampulla,  and  opens  by  both  ends  into  the  vestibule.  The 
three  canals  are  called :  1st,  superior,  which  is  vertical  in 
direction  and  produces  the  ridge  seen  on  the  anterior  face  of 
the  petrous  bone  ;  2nd,  the  posterior,  or  oblique,  which  is 
also  vertical ;  3rd,  the  external,  or  horizontal.  These  three 
canals  present  but  five  openings  into  the  vestibule,  owing 
to  the  fact  that  the  posterior  and  superior  have  a  common 
opening-  into  the  posterior  corner  of  the  vestibule.     The  other 


510  DESCRIPTIVE  ANATOMY.    " 

Opening's  were  mentioned  in  the  description  of  the  vestibule — 
three  being*  into  the  posterior  and  two  into  the  superior  corner. 

The  Cochlea. 

The  cochlea  lies  in  front  of  the  vestibule  and  by  its  base 
forms  the  promotory,  seen  on  the  inner  wall  of  the  tympanum. 
When  entire  it  resembles  a  snail's  shell  and  may  be  discribed 
as  consisting-  of  a  tube  divided  into  two  apartments  by  a  longi- 
tudinal septum,  one  end  of  the  tube  being-  closed  and  much 
smaller  than  the  open  end  from  which  it  rapidly  tapers.  The 
septum  is  not  complete,  for  it  fails  to  reach  to  the  small, 
closed  end,  thus  allowing-  a  communication  between  the  two 
chambers.  This  tube  is  coiled  by  two  turns  and  a  half  around 
a  stem,  or  tapering-  pillar,  called  the  modiolus.  The  septum 
subdividing-  the  two  chambers,  which  are  called  seals,  is 
named  the  lamina  spiralis.  It  consists  of  two  layers,  between 
which  is  a  narrow  space,  called  scala  media,  and  it  terminates 
in  a  hook-like  projection  called  the  hamulus.  When  examined 
closely  the  lamina  spiralis  is  seen  to  consist  of  three  structures; 
the  portion  next  the  modiolus  is  bony,  farther  out  it  is  mem- 
br2,nous  and  the  utermost  portion  is  muscular  and  sometimes 
called  the  cochlearis  muscle.  The  small  space,  existing-  be- 
tween the  extremity  of  the  lamina  spiralis  and  the  cupola,  is 
called  the  helicotrema ;  it  establishes  communication  between 
the  two  chambers,  one  of  which  is  called  the  scala  tympani, 
the  other  the  scala  vestibuli.  The  scala  vestibuli  is  seen  to 
communicate,  at  the  base  of  the  cochlea,  next  the  vestibule, 
with  the  anterior  corner  of  the  vestibule.  The  scala  tympani 
communicates  with  the  tympanum,  by  means  of  the  fenestra 
rotunda.  The  modiolus  is  the  tapering-  pillar  around  which 
the  two  scalae  wind.  In  its  centre  there  is  a  canal  called  the 
tubulus  centralis  modioli.     Its  base  is  next  the  vestibule. 

The  Membranous  Labyrinth. 

Beside  the  parts  above  described,  the  labyrinth  contains 
others  for,  within  each  semicircular  canal  is  a  membranous 
counter  part,  two  thirds  smaller,  separated  from  the  bony 
wall  by  liquid.  The  membranous  canals  present  the  same 
dilations  at  one  end,  ampulla,  as  the  bony. 


THE  ORGAN  OF  HEARING.  511 

In  the  vestibule  also  are  two  membranons  sacs,  one  above 
the  other.  The  upper  one  receives  the  opening's  of  all  the 
semicircular  canals  and  lies  in  the  fovea  hemi-elliptica.  It  is 
called  utriculus,  or  sacculus  proprius.  In  the  membranous 
labyrinth,  as  the  above  parts  are  collectively  called,  are  found 
crystalline  particles,  carbonate  and  phosphate  of  lime,  called 
ear-dust,  or  otoliths. 

The  auditory  nerve  gains  the  labyrinth  through  the  internal 
auditory  meatus.  At  the  bottom  it  divides  into  a  vestibular 
and  a  cochlear  branch,  the  latter  dividing  into  filaments  which 
run  in  channels  in  the  modiolus  and  turn  outward  to  ramify 
in  the  lamina  spiralis.  The  vestibular  branch  divides  into 
three,  one  for  each  of  the  membranous  sacs,  and  one  for  the 
semicircular  canals. 


512  DESCRIPTIVE  ANATOMY. 


THE  OEGAN  OF  VISION. 

The  org-an  of  vision  is  situated  in  the  orbits,  two  conical 
cavities  found  on  the  face.  Like  the  organ  of  hearing,  it 
consists  of  two  similar  portions,  one  on  each  side,  called  the 
eye-ball  and  its  appendages. 

The  Appendages  of  the  Eye. 

The  Appendages  of  the  eye,  tutamina  oculi,  are  mere 
accessories  to  the  true  organ  of  vision,  the  eye-ball,  for  the 
purpose  of  protection  and  ornament.     They  are: 

JSyebrozu  is  a  prominence  of  the  integument,  curved,  covered 
with  hair  and  situated  above  each  orbit.  They  are  intended 
for  ornament  and  protection  from  dust,  perspiration  and  too 
vivid  light,  and  to  break  the  force  of  any  blow  falling  on  the 
front  of  the  orbit. 

The  eyelids  consist  of  two  movable  curtains,  which  are 
constantly  playing  over  the  front  of  the  eye-ball.  The  aper- 
ture, which  separates  the  two  lids,  one  called  upper,  superior 
palpebra,  the  other  lower,  inferior  palpebra,  is  known  as  the 
palpebral  fissure  and  can  be  extinguished,  or  dilated  atpleasure. 
The  two  lids  meet  externally  at  an  acute  angle  called  the 
external  canthus;  internally  when  they  seem  about  to  meet 
they  refrain  from  doing  so  and  the  interval  between  is  pro- 
longed inward  towards  the  nose  for  some  distance  before 
forming  the  internal  canthus.  The  triangular  space  thus  left 
between  the  lids  at  the  inner  canthus  is  called  the  lachrymal 
lake,  lacus  lachrymalis,  in  which  is  seen  a  reddish,  conical 
projection,  called  the  caruncle,  which  is  bounded  externally 
by  a  curved  fold  of  mucous  membrane,  called  the  plica  semi- 
circularis.     The  concavity  of  this  fold  is  external. 

At  the  commencement  of  the  lachrymal  lake,  just  where  the 
two  lids  are  apparently  about  to  unite,  there  is  a  projection 
from  the  edge  of  each  lid,  called  the  lachrymal  papilla,  or 
tubercle,  on  the   summit  of  each  of  which  is  an   opening,  the 


THE  ORGAN  OF  VISION.  513 

punctum  lachrymale.  The  free  edg-e  of  each  lid  is  provided 
with  several  rows  of  short  curved  hairs,  the  eye-lashes,  in- 
tended for  ornament,  to  render  the  contact  of  the  lids  more 
intimate  and  to  protect  ag"ainst  dust,  etc.  In  structure  the 
eye-lids  consist  of  the  following-  parts:  externally  there  is  a 
layer  of  thin,  loose  skin  with  subjacent  areolar  tissue;  inter- 
nally, a  layer  of  mucous  membrane  called  the  conjunctiva, 
which  not  only  lines  the  inner  surface  of  the  lids,  but  is 
reflected  over  the  front  of  the  ball  —  palpebral  and  ocular 
portions.  The  palpebral  portion  is  studded  with  papillae. 
Just  beneath  the  integfument,  on  the  outer  surface  of  the  lid, 
is  a  pale  thin  muscle,  the  orbicularis  palpebraum,  so  named 
from  the  fact  that  it  is  somewhat  round,  passes  from  one  lid  to 
the  other  and  surrounds  the  palpebral  fissure,  its  function  is 
to  close  the  lids.  Beneath  the  orbicularis  palpebrarum,  in  each 
lid  is  a  curved  plate  of  cartilage,  about  an  inch  in  length,  called 
the  tarsal  cartilage.  The  superior  is  the  larger  and  is  semi- 
lunar in  shape;  the  inferior  is  much  the  narrower  and  oval. 
The  two  are  attached  along  their  circumference  to  the  edge  of 
the  orbit  by  ligamentous  fibres.  Externally,  they  are  held  to 
the  outer  angle  of  the  orbit  by  a  ligament  called  the  external 
palpebral,  or  tarsal  ligament;  internally,  they  terminate  in  a 
ligament,  called  the  tendo  oculi,  which  holds  them  to  the  edge 
of  the  orbit.  Lying  on  the  posterior  surface  of  the  lids  be- 
tween them  and  the  mucous  membrane,  and  opening  on  the 
edge  of  the  lids  is  a  number  of  vertical,  beaded  bodies,  the 
Meibomiam  glands,  the  secretion  from  which  is  discharged  on 
the  edge  of  the  lids.  There  are  thirty  of  these  glands  for  the 
upper  lid,  but  a  smaller  number  for  the  lower. 

Lachrymal  apparatus.  Lying  in  the  depression,  seen,  on 
the  orbital  plate  of  the  frontal  bone,  just  behind  the  external 
angular  process,  is  the  lachrymal  gland.  It  is  about  the  size 
and  shape  of  an  almond  and  rests  on  the  posterior  part  of  the 
upper  tarsal  cartilage.  The  ducts,  seven  to  twelve  in  number, 
which  convey  the  secretion  of  the  gland,  tears,  being  dis- 
charged on  the  surface  of  the  conjunctiva,  is  constantly  swept 
toward  the  inner  canthus  of  the  eye  by  the  frequent  movement 
of  the   lid;  there  it  disappears   in  the  lachrymal    puncta  from 


514  DESCRIPTIVE  ANATOMY. 

each  of  which  there  leads  a  small  canal  called  the  lachrymal 
canaliculi.  The  upper  first  ascends,  then  bends  inward  to 
terminate  in  the  nasal,  or  lachrymal  duct;  the  lower  first  de- 
scends, then  turns  inward  to  terminate  in  the  nasal  duct  beside 
the  superior.  The  nasal  duct  extends  a  little  way  above  the 
opening's  of  the  canaliculi  in  a  portion,  called  the  lachrymal 
sac;  and  from  this  point  the  duct  extends  downward,  outward 
and  slig"htly  backward   to  terminate  in  the  inferior  meatus  of 

the  nose. 

The  Globe  of  the  Eye. 

The  eye-ball  is  situated  in  the  front  part  of  the  orbit,  em- 
bedded in  a  mass  of  fat.  It  is  nearly  g-lobular,  its  antero- 
posterior diameter  being"  one  inch  and  its  transverse  seven- 
twelfths  of  an  inch.  Posteriorly  it  receives  the  optic  nerve, 
at  a  point  about  one  one-tenth  of  an  inch  to  the  nasal  side  of 
the  centre.  The  ball  consists  of  concentric  layers  enclosing-  a 
bag-  of  liquid ,  which  forms  about  four-fifths  of  it.  These  coats 
or  layers  are  sclerotic,  choroid  and  retina. 

The  Sclerotic  Coat. 

The  sclerotic,  familiarly  known  as  the  white  of  the  eye,  is 
a  dense  fibrous  membrane,  which  serves  as  a  protecting"  enve- 
lope for  the  rest  of  the  eye-ball.  Its  anterior  one- sixth  is 
wanting",  the  aperture  being"  filled  by  a  transparent  membrane, 
the  cornea.  Posteriorly  the  sclerotic  is  perforated  by  the 
optic  nerve,  not  en  masse,  for  the  nerve  splits  into  a  number 
of  fibres,  which  pierce  the  coat  separately,  producing"  the 
appearance  known  as  macula,  or  lamina  cribrosa,  the  fibrous 
sheath  of  the  nerve  becoming"  continuous  with  the  sclerotic, 
while  in  front  the  sclerotic  is  continuous  with  the  cornea. 

The  Cornea. 

The  cornea  forms  the  anterior  one-sixth  of  the  first  invest- 
ment of  the  eye-ball.  It  forms  a  seg-ment  of  a  smaller  sphere 
than  the  sclerotic  and  being"  more  convex  it  causes  the  increase 
of  the  antero-posterior  diameter  over  the  transverse.  The 
cornea,  instead  of  being"  opaque,  like  the  sclerotic,  is  transpa- 
rent and  its  circumference  is  received    beneath  the  anterior 


THE  ORGAN  OF  VISION.  515 

bevelled  edge  of  the  sclerotic  with  which  it  is  continuous  in 
some  of  the  structures.  It  consists  of  five  layers.  The  ante- 
rior surface  is  an  epithelial  layer,  derived  from  the  conjunc- 
tiva ;  the  posterior  layer  is  also  epithelial,  the  lining-  membrane 
of  the  anterior  chamber.  Next  each  of  these  is  found  a  layer 
of  elastic  tissue,  the  two  la3^ers  constituting-  what  is  called 
the  elastic  cornea,  and  separating-  these  is  a  layer  of  fibrous 
tissue,  called  the  cornea  propria,  which  can  be  split  into  sixty 
layers  of  spindle-shaped  cells  with  branching  intervals,  in 
w^hich  circulates  the  colorless  plasma  of  the  blood.  It  is  with 
this  cornea  propria  that  the  sclerotic  is  continuous.  The 
cornea  is  of  varying-  convexity  in  different  people  and  at  differ- 
ent periods  of  life.  It  is  more  convex  in  youth  and  becomes 
less  so  in  old  age,  at  which  period  there  is  often  seen  around 
the  cornea  a  yellowish  band,  called  arcus  senilis. 

The  Choroid. 

The  c/207-o?d  Wes  within  the  sclerotic,  with  which  it  is  con- 
nected by  areolar  tissue,  sometimes  called  lamina  fusca,  which 
is  pierced  by  the  optic  nerve.  At  the  point  in  front  where 
the  sclerotic  ceases  the  choroid  terminates  in  a  flattened  mem- 
brane, the  iris,  which,  in  its  centre  presents  a  round  aperture, 
the  pupil.  The  choroid  consists  of  three  layers,  the  outer 
two  red  and  the  inner  black.  Between  the  two  red  and  the 
black  layers  some  make  a  fourth  layer,  the  membrana  limitans- 
The  external  red  layer  is  called  the  venous  layer;  the  interna^ 
red  layer  the  capillary,  arterial,  layer,  or  the  tunica  Ruyschiana. 
The  internal  layer,  or  membrana  pigmenti,  or  tapeta  is  of  a 
black  color,  consisting  of  cells,  filled  with  coloring  matter. 
On  the  anterior  surface  of  the  choroid,  just  around  its  anterior 
margin,  is  a  whitish  band,  one-fortieth  of  an  inch  wide,  called 
the  ciliary  ligament,  which  binds  together  the  cornea  and 
sclerotic  and  the  choroid  and  iris.  Extending  back,  about  one- 
eig-hth  of  an  inch,  on  the  anterior  aspect  of  the  choroid,  is  a 
gray  circular  band,  called  the  ciliary  muscle.  On  the  poste- 
rior aspect  of  the  front  of  the  choroid  are,  about,  sixty  ridges, 
diverging-  from  the  rim  of  the  choroid,  called  the  ciliary 
processes. 


516  DESCRIPTIVE  ANATOMY. 


The  Iris. 

The  iris  is  the  thin  flat  membrane,  which  continues  the 
choroid  in  front.  In  its  centre  is  seen  the  opening-,  called  the 
pupil.  The  various  colors  of  the  iris  are  due  to  the  difference 
of  color  of  the  pig-mentary  matter  found  in  its  cells  and  to 
the  varying-  arrang^ement  of  the  blood  vessels.  The  color  is 
darkest  usually  near  the  centre. 

Towards  the  middle  of  the  iris  is  a  circle  of  little  shaggy 
projections.  The  foundation  of  the  structure  of  the  iris  is 
fibrous  tissue,  consisting- of  circular  and  radiating-  fibres  inter- 
posed between  which  are  pig-ment  cells.  In  front  and  behind 
this  fibrous  layer  is  a  layer  of  pig-ment  cells.  In  the  iris 
are  also  seen  unstriated  muscular  fibres,  circular  around  the 
pupil  and  radiating-  toward  the  circumference:  by  the  action 
of  these  fibres  the  pupil  is  constantly  dilating  and  contracting-. 
Blood  vessels  and  nerves  ramify  throug-hout  the  structure. 
On  the  posterior  surface  the  iris  consists  of  a  black  layer, 
called  the  uvea,  which  is,  in  fact,  a  continuation  of  the  mem- 
brana  pigmenta  of  the  choroid. 

Anterior  Chamber — Between  the  iris  and  pupil  behind,  and 
the  cornea  in  front  is  a  small  cavity,  called  the  anterior  cham- 
ber. 

Posterior  Chamber — Between  the  iris  and  pupil  in  front, 
and  the  lens  behind  is  another,  smaller  cavity,  called  the  pos- 
terior chamber.  These  two  contain  a  liquid,  called  the  aque- 
ous humor,  and  they  communicate  throug-h  the  pupil,  after 
the  sixth  month  of  foetal  life,  up  to  which  time  the  pupil,  is 
closed  by  a  membrane,  called  the  papillary.  Both  chambers 
are  lined  by  a  membrane  which  secretes  the  aqueous  humor. 

The  Retina. 

The  retina  is  the  innermost  of  the  three  coats  of  the  eye, 
lying-  just  within  the  choroid.  It  is  wanting-  in  front  even 
for  a  g-reater  distance  than  the  two  preceding-  layers,  for  it 
ceases,  as  it  reaches  the  ciliary  processes  in  a  roug-h  jag-ged 
marg-in,  called  ora  serrata,  and  is  continued  thence  to  the  crys- 
talline lens  by  a  vascular  membrane,  called  the  suspensory 
ligament  of  the  lens.     The  outer  surface   of  the  lig-ament  is 


THE  ORGAN  OF  VISION.  517 

fluted  to  correspond  with  the  ciliary  processes,  ag'ainst  which 
it  rests. 

The  retina  is  non-resisting-  and  translucent,  being  partially 
formed  by  the  expansion  of  the  optic  nerve,  with  which  it  is 
continuous  posteriorly. 

Exact!}'  in  the  centre,  posteriorly,  is  a  round,  yellowish  spot, 
called  the  macula  lutea,  and  in  the  centre  of  this  spot  a  depres- 
sion called  fovea  centralis.  About  one-tenth  of  an  inch  to  the 
inner  side  of  this  is  seen  the  termination  of  the  optic  nerve — 
optic  disk,  or  papilla— showing-  in  its  centre  the  arteria  centralis 
retinae,  breaking-  up  into  branches.  From  this  point  forward 
the  retina  gradually  thins  to  its  termination. 
The  Vitreous  Humor. 

Just  within  the  retina  is  a  bag,  called  the  hyaloid  membrane, 
containing  a  liquid,  called  vitreous  humor.  This  is  similar  in 
composition  to  the  aqueous  humor,  being  98%  water.  Travers- 
ing the  centre  of  this,  in  the  foetus,  is  a  branch  of  the  arteria 
centralis  retinae,  making  its  way  to  the  lens,  called  the  capsular 
artery.     It  disappears  at  birth. 

The  Crystalline  Lens. 

Indenting  the  front  of  the  hyaloid  membrane  is  found  a 
doubly  convex  transparent  body,  called  the  crystalline  lens. 
Its  posterior  surface  is  much  more  convex  than  the  anterior, 
the  latter  forming  the  posterior  wall  of  the  posterior  chamber. 
The  lens  forms  only  the  bulging  portion  of  the  wall,  the 
circumference  of  which  is  formed  by  the  suspensor}'  ligament 
of  the  lens,  which  extends  from  the  ora  serrata  of  the  retina 
to  the  rim  of  the  lens.  This  ligament  is  formed  of  two  layers 
and  when  it  lays  hold  of  the  lens  it  leaves  a  circular  canal  around 
it,  called  the  canal  of  Petit.  The  lens  is  invested  b}''  a  trans- 
parent homogeneous,  elastic  membrane,  the  capsule  of  the  lens. 
In  structure  the  lens  consists  of  a  series  of  concentric  layers 
of  parallel  fibres,  which  gradually  harden  towards  the  centre 
of  the  lens.  It  can  also  be  splitinto  three  triangular  segments, 
which  meet  by  their  apices  in  the  centre  of  the  lens. 

In  youth  the  lens  is  more  convex  and  much  softer  than  in 
old  age,  as  it  gradually  becomes,  with  advancing  life,  firmer 
and  less  convex. 


iis:db:x:. 


Abdomen,  boundaries  of, 161 

lymphatics  of, 386 

muscles, 214 

reg-ions 161 

viscera  of , 161-193 

Abdominal  aorta, 328 

branches   of, 330 

ring",  external, 215 

"      internal, , 495 

viscera,   relations  of, 161-177 

Abducent  nerve, 467 

Abductor  minimi  digiti  (hand), 256 

"     (foot) 275 

poUicis  (hand), 256 

"       (foot), 275 

Accelerator  urinae, 488 

Accessorius  muscle, 275 

Acetabulum, 39 

Acromial   muscle, 237 

thoracic  artery, 310 

Acromio-clavicular  joint, 120 

Acromion  process, 20 

Alai  of  vomer, 76 

Alar  ligaments, , 143 

thoracic  artery, 310 

Alimentary  canal, 177-182 

Al veolar  process,  lower  ja w 84 

upper  jaw, 81 

Anconeous  muscle, 252 

Angle,  jaw, 85 

pubes 38 

rib, , 14 


520  INDEX. 

Atigfular  convolutions, 397 

movements, Ill 

process,  external  and  internal, 61 

Ankle  joint, 146 

Anuulus  ovalis, 210 

Anterior  ethmoidal  cells, 73 

fossa  skull, 93 

reg"ion  skull, 95 

Antitrag-us, 504 

Antrum  of  Highmore, . . . : 78 

Anus, 182 

Aorta, 321 

abdominal, 328 

branches  of, 330 

arch  of, 321 

descending-, 32b 

Aortic  opening-  diaphrag-m, 220 

semilunar  valve, 211 

sinuses, 212 

Appendages  of  eye, 512 

Appendix,  right  auricle, 209 

left  auricle, 211 

vermiform, 168 

Aqueductus  vestibuli, 64 

Fallopii, 65 

Sylvius, 408 

Aqueous  humor, 516 

Arachnoid  of  brain, 391 

cord ' 417 

Arm,  arteries  of,  .  . 304 

fascia, ; ^- 241 

lymphatics 387 

muscles, 241 

nerves, 429-438 

veins, 374 

Artery,  or  arteries  : 

acromial  thoracic, 310 

alar  thoracic 310 


I 


INDEX.  521 

Artery,  or  arteries  (  Continued)  : 

ang-ular, 294 

anterior  cerebral, , 364 

choroid, 364 

ciliary, 363 

communicating- 364 

articular  of  knee, 349 

axillary, 307 

basilar, 304 

brachial, 312 

calcanean, 351 

carotid,  common,  left. 324 

rig-ht 287 

external 290 

internal, 360 

circumflex,  arm, 211 

thig-h, 347 

colica  dextra, 336 

media 336 

sinistra, 337 

coronary,  heart, 323 

'^  lips, 294 

dig-ital, 318 

epig-astric, 342 

facial 293 

femoral 343 

deep 345 

g-astric 332 

g-astro-epiploica  dextra, 333 

sinistra, 334 

j^^luteal, 359 

hepatic 333 

ileo-colic 336 

iliac,  common, 340 

external,  .  .  .  : 341 

internal, 355 

innominata ■.  . ..  323 


5<22  INDEX. 

Artery,  or  arteries  (Continued)  : 

internal  mammary ,.....,....,.,,,,  306 

maxilllary, ..,.,. 297 

plantar, 352 

intestini   tenuis, ,  , 33S 

lateralis  nasi, , 294- 

ling-ual, , , . , , 295 

long- thoracic,... ,..  .    .., , ,.  311 

obturator, , »  .  , .  . .  356 

occipital, , 295 

opthalmic, 362 

plantar, . ,  , 352 

perineal, 358 

peroneal , 351 

phrenic, 330 

radial,  forearm, 315 

hand  and   wrist, 318 

renal, 340 

sciatic, . , 351 

temporal,  superficial, 296 

deep, 298 

thyroid  axis, 304 

tibial,  anterior, 353 

tibial,  posterior, 350 

transversalis  colli, 305 

ulnar,  forearm, 315 

"     hand, 316 

vertebral, 304 

Articulations  in  g-eneral, 108 

Articulation,  ankle, 146 

atlo-axoid 114 

calcaneo-astrag-aloid, 148 

cuboid, 148 

carpal, 129 

costo-vertebral, 150 

costo-sternal 132 

elbow, 125 


INDEX.  523 

Articulation,  ( Coyitinued)  : 

hip, 134 

knee 139 

occipitoatloid, 115 

pelvis, 132 

Articulation,  radio-carpal,  (wrist) 127 

ulnar, 124 

shoulder, 121 

sterno-clavicular, 118 

temporo-maxillary, 130 

tibio-fibular, 145 

vertebral  column, 112 

wrist, 127 

Arytenoid  cartilage, 195 

Ascending"  colon, 168 

Astragfalus, 51 

Atlas, 6 

Auditory  nerve, 464 

Auricle,  of  ear 504 

heart 209-211 

Axilla, 502 

Axillary  artery, 307 

vein, 366 

Axis, 7 

B. 

Back,   muscles  of, 230 

Base  of  brain, 401 

skull,  superior  surface, 92 

inferior  surface, 89 

Basilic  vein, 375 

Bicipital  fascia, 242 

g-roove, 21 

Bladder,  relations  in  female, 176 

male, 175 

description  of, 189 


524  INDEX. 

Bone,  or  Bones:  1-107 

astragalus, 51 

atlas, 6 

axis, 7 

calcaneum, = 50 

carpal, 27 

clavicle 16 

coccyx, 10 

cranial , 57 

cuboid 52 

ethmoid, 72 

articulations  of, 102 

femur, 46 

fibula 48 

frontal, 60 

articulations  of, 100 

humerus -. 20 

hyoid, 106 

ilium, 35 

inferior  maxillary, 106 

turbinated , 75 

articulations  of, 105 

innominata, 35 

ischium, 37 

lachrymal 74 

malar, 77 

articulations  of, 106 

nasal 74 

articulations  of, 103 

occipital, 58 

articulations  of, 99 

palate, 81 

articulations  of 104 

parietal 59 

articulations  of, 100 

patella, 45 

radius 25 


INDEX.  525 

Bone,  or  bones,  (Continued)'. 

rib, 13 

sacrum , 8 

scaphoid 53 

scapula, 17 

sphenoid, 66 

sphenoid,  articulations  of, 101 

sternum, 11 

superior  maxillary, 78 

articulations  of, .... 103 

temporal, 26 

articulations  of, 101 

tibia, 45 

ulna, 23 

vomer, 76 

articulations  of, 105 

Brain, 392 

base  of 401 

convolutions, 363 

interior, 403 

membranes, 389 

Bronchi, 204 

c. 

Canal,  auditory, 504 

Capsular  lig-ament,  hip, 134 

shoulder, 121 

Cartilage,  arytenoid, 201 

cricoid, 197 

Cava,  inferior, 369 

superior 383 

Cerebellum, 415 

Cerebrum 392 

Clavicle 16 

Cfjeliac  axis, 331 

Coraco-acromial  ligament, 121 

clavicular, 120 

Corpus  callosum, 404 

fimbriatum 406 


526  INDEX. 

Costal  cartilages, ,....,...  15 

Cranial  bones, 57 

nerves, 458 

Cranial  nerves,  eigbth 469 

eleventh ■••... 474 

fifth, . , 462 

first, 460 

fourth, 462 

ninth, 470 

second, 461 

seventh, 467 

sixth, 467 

tenth, , 471 

third, 461 

twelfth, 474 

Crystalline  lens, 517 

Ear,..  ,... ' ••  ■    503 

Elbow,  bend  of ........ . 313 

joint, 125 

Epididymis, 195 

Epiglottis, 198 

Ethmoid  bone, 72 

articulations  of, 102 

Eye, 512 

tunics  of, 514 

muscles  of, 281 

F. 

Pace,  arteries  of 293 

bones, 74 

muscles, -. 277-285 

Fauces,  isthmus  of, 152 

Female  generative  organs, 490 

Femoral  artery, 343 

canal, ...    499 

hernia, 499 

Fifth  nerve, 462 

First  nerve, 460 


INDEX.  527 

Fissure  of  brain, 393 

Foot,  arteries  of 351-351-267 

bones, ^^ 

muscles, -73 

ligaments,    147-150 

nerves, 453-323 

Fossa,  spheno-maxillary 89 

of  skull,  anterior, 91 

middle  and  posterior, 91 

temporal, °° 

zygomatic, °° 

G. 

Ganglion,  cervical, 4-/6 

ciliary,  or  opthalmic, 482 

Meckel's 483 

otic 484 

semilunar, 480 

H. 

Hand,  bones  of ,  . .  .    2^ 

ligaments, ....    •  •    •    129 

Heart 207 

Hernia,  femoral, 439 

inguial, 494 

Hip  joint, 1*^4 

I. 

Ileum, 167 

Iliac  arteries,  common 340 

external, •  • .  341 

internal, 355 

veins,  external, 368 

internal 369 

Ilium, .  •  ■ 35 

Inferior  vena  cava,          369 

Inguinal  canal 406 

hernia, 494 


528  INDEX. 

Intestine,  large,  description  of, 178 

small,  discription  of, 178 

relations  of • 166 

Iris,  small  divisions  of ....■•• 516 

Ischio-rectal  reg^ion, 486 

Ischium, 37 

Island  of  Reil, 399 

K 

Kidney  relations  of, 187 

structure  of, 188 

Knee  joint, 139 

L. 

Larynx,  cartilages  of , . . 196 

ligaments  of, •  ■  • 199 

muscles  of, 200 

Ligaments: 

acromio-clavicular, 120 

ankle, 146 

atlanto-axoid, 114 

calcaneo-astragaloid, 148 

cuboid, 148 

scaphoid, 149 

common  vertebral 112-114 

costo- vertebral, ■        ....  150 

of   elbow,.. 125 

of  hip, 134 

of  jaw^, 130 

of  knee, 139 

radio-carpal, 127 

radio-ulnar, 124 

sacro  sciatic 133 

of  shoulder,  . .  . .  : 121 

tibio-fibular 145 

Liver,  relations  of 171 

structure  of, 185 

Lungs,  relations  of , 205 

structure  of, 205 


INDEX.  529 

Tvymphatics  :  V 386 

arm 387 

cervical, 388 

lower  extremity, 387 

thorax,.... 388 

M. 

Malar  bone,..., 77 

articulation  of, 106 

Manubrium 12 

Mediastinum 207 

Medulla  oblong-ata, 410 

Membranes  of  brain, 380 

cord, 417 

Munro,    foramen  of 409 

Mouth 151 

Muscle,  or  Muscles  :  213 

abductor  minimi  dig-iti  (hand), 256 

(foot), 275 

poUicis  (hand), 255 

hallucis, 275 

accessorius, 275 

adductor  brevis, 267 

long-US, 266 

mag-nus, 267 

anconeus, 252 

arytaenoideus, 261 

biceps  (arm), 242 

(thig-h), 261 

brachialis  anticus, 243 

buccinator, 203 

compressor  naris 276 

constrictor  pharyng^eus,  inferior 157 

medius, 158 

superior, 158 

coraco-brachialis, 242 

crico-arytoenoideus  lateralis, 201 

posticus  201 


530  INDEX. 

Muscle,  or  Muscles,  (Continued)  : 

crico-thyroid, ..,,,..  200 

deltoid, 237 

diaphrag-m,... .  219 

dig-astric, .  225 

erector  spinae...... 233 

extensor  brevis  dig-itorum, 273 

extensor  carpi  radialis  brevior, ...... 250 

longior, 250 

ulnaris, .  252 

communis  digfitorum 251 

indicis,.... 254 

long-US  digitorum,... ...   270 

minimi  dig-iti, 252 

ossis  metacarpi   pollicis, 253 

primi  internodli  pollicis, 253 

proprius  pollicis, 272 

of  face...... 277 

flexor  brevis  minimi  dig-iti,  (hand),..  — 256 

(foot), 276 

digitorum, 275 

pollicis  (hand),... 255 

(foot),. 276 

flexor  carpi  radialis, 246 

ulnaris, 247 

long-US  dig-itorum, 270 

pollicis  (hand),... 248 

(foot),..... 270 

ossis  metacarpi  pollicis, 255 

profundus  digitorum, 248 

sublimis  dig-itorum 247 

gastrocnemius, 268 

gemellus,  superior, 258 

inferior, 259 

g-enio-hyo-g-lossus, 226 

g-enio-liyoid,.... 226 

gluteus  maximus, 257 

medius, 258 


INDEX.  531 

Muscle,  or  Muscles,  (Continued): 

minimus 259 

ofracilis ..  = 263 

of  hand .  254 

of    hip, 237 

iliacus 264 

infraspinatus, 239 

intercostal •  ■  • 235 

of  larynx,... 200 

latissiraus  dorsi, _ 231 

levator  ang-uli  scapulae 231 

long-US  colli, 229 

masseter, •. 283 

mylo-hyoid 226 

of  neck 222-229 

obliquus  abdominus  externum 214 

internus, 216 

obturator  externus, 260 

internus, 219 

omo-hyoid, 225 

of  palate, 156 

pectineus, , .  266 

pectoralis  major, 235 

minor, 236 

of  perineum, ■  • 488 

peroneus  brevis 273 

long-us, 272 

plantaris, 269 

platysma  myoides, 223 

popliteus, 269 

pronator  quadratus, 248 

radii  teres, 246 

psoas  maj^nus, 263 

pteryg-oid,   external, 284 

internal, 285 

pyramidalis  abdominis 218 

pyriformis, 258 


532  INDEX. 

Muscle,  or  Muscles,  (Continued)  : 

quadratus  femoris, 259 

lumborum 221 

rectus  abdominis, . ...    217 

rectus  capitis  auticus  major, 229 

minor 229 

lateralis, 229 

femoris, 263 

rhomboid, 232 

sartorius, 262 

scalenus  anticus 228 

posticus, 229 

semimembranosus 261 

semitendinosus, 261 

serratus  mag^nus, 237 

posticus,  inferior, 232 

superior, 232 

soleus, 269 

splenius, 233 

sterno-cleido-mastoiu ^ 223 

sterno-hyoid, 224 

sterno-thyroid, 224 

stylo-hyoid, 226 

stylo-pharyng-eus,    158 

subclavius, 236 

subscapulars, 238 

supinator  brevis, 251 

long-US, 250 

supraspinatus, 239 

temporal, 284 

teres  major, 240 

minor 240 

thyro-aryt^noideus, 201 

thyro-hyoid, .' 224 

tibialis  anticus, 271 

posticus, ......  270 

transversalis  abdominis, ......  216 

trapezius 230 


INDEX.  533 

Muscle,  or  Muscles,  ( Contiimed )  : 

triceps  extensor  cubiti, .    .  . 243 

cruris, 263 

vastus  externus. . 265 

internus, 265 

N. 

Nares,  anterior, 95 

posterior, 96 

Nasal  bones, 74 

articulations  of, 103 

Neck,  muscles   of, 222-229 

triangles  of, 227 

veins  of, 281-282 

Nerves,  or  Nerve  : 421 

anterior  crural, 443 

anterior  interosseus, 435 

auditory, 469 

auricularis  magnus, 424 

chorda  tympani,        . 468 

ciliary, 464 

circumflex, 438 

cranial, ....    458 

dental,  anterior 465 

inferior, 466 

posterior, .... 465 

descendens  noni, 475 

dorsal  spinal, 439 

eighth  pair, .    469 

eleventh  'pair, 474 

external  cutaneous, 442 

facial, 467 

fifth,. .  .    462 

fourth, 462 

frontal. 464 

genito-crural, 442 

glosso-pharyngeal, 470 

gluteal,  superior 446 

great  petrosal, 468-484 


534  INDEX. 

Nerves,  or  Nerve,  (Continued)  : 

g-ustatory, 446 

hypoo-lassal, 474 

ilio-hypog-astric, 441 

ilio-ing-uinal,    ... ...  465 

intercostal, .  439 

intercosto-humeral, , ,  , 431-439 

internal  cutaneous, 443 

lachrymal, 463 

larynofeal,  recurrent, , 473 

superior, 473 

lesser  sciatic, 448 

long-  saphenous, 444 

lumbar, 440 

' '       plexus, 440 

lumbo-sacral, 445 

maxillary,  inferior, 469 

superior, 464 

median, 434 

middle  cutaneous, , 443 

musculo-cutaneous  (arm), 430 

(leg-), 456 

musculo- spiral, 436 

ninth, 470 

obturator, 443 

occipital,  small, 424 

olfactory, 460 

opthalmic, 463 

optic, 461 

orbital, 464 

perineal, 448 

peroneal, 456 

phrenic, 425 

plantar,  external, 453 

internal, 453 

pneumog-astric, 471 

popliteal,   external, 454 

internal, 450 


INDEX.  535 

Nerves,  or  Nerve,  (Continued)  : 

posterior  interosseous, 437 

pudic,  internal, 447 

radial, 437 

recurrent  laryng-eal, 473 

sacral  plexus 445 

saphaneous,  long- 444 

short 45 

sciatic,  great, 44 

small, 449 

sixth, 467 

spinal ,  accessory, ,  474 

splanchnic,  great, 480 

small, 480 

subscapular, 429 

superficialis  colli, 423 

suprascapular, 428 

sympathetic, 476 

tenth, 471 

third, 401 

thoracic,  anterior, ,  429 

posterior, 428 

tibial,  anterior 455 

posterior, 452 

twelfth, 474 

ulnar, 432 

vagus |71 

O. 

<^)bturator  artery 356 

externus  muscle 260 

internus, ....  259 

Occipital   artery, 295 

bone, 58 

articulations  of, 99 

fossa 94 

Occipito-atlantal  articulation 115 

Occipito-axial, 116 


536  INDEX. 

Oesophagus, 159 

Omentum,  great 164 

lesser, ■  • 164 

Orbit, .  .        96 

Orbit,  arteries  of,... 362 

muscles  of, 281 

Os  calcis, 50 

innominatum, -.  35 

Ovary, • • • • 492 

P. 

Palate  bone, • ■  • 81 

articulations  of, 104 

hard,.. 90 

muscles  of, 156 

Palmar  arch,  deep, 320 

superficial, 316 

Pancreas,  relations  of, 173 

structure  of...... 186 

Parietal  bones, .  39 

articulations  of, 100 

Patella,-... 45 

Pelvis 40 

Penis 193 

Perineum,. 488 

Peritoneum, 163 

Pharnyx 153 

Pleura, 206 

Pouch  of  Douglas, 491 

R. 

Radial  artery,  arm '. 315 

forearm,    318 

nerve,  437 

Radius 25 

Rectum,  relations  of,   female, 492 

male, 170 

structure  of 180 

Renal  artery, 340 


INDEX.  537 

Retina 516 

Ribs 13 

Rino^.  abdominal  external,    495 

internal, 495 

crural,  or  femoral, 499 

S. 

Sacral  arteries 359 

foramina, 9 

plexus 445 

Sacrum 8 

Scaleni  muscles, 228 

Scapula 17 

Scarpa's  triangle 267 

Sciatic  artery 357 

nerve,  g"reat 449 

lesser 448 

Shoulder  joint, 121 

Skull,  anterior  reg-ion, 95 

base  of,  lower  surface 89 

upper  surface, 92 

lateral  region, 87 

vertex 87 

Soft  palate 152 

Spermatic  artery 339 

canal .       495 

Sphenoid  bone, 66 

articulations  of, 101 

Sphenoidal   fissure ...       95 

Spinal  cord 417 

nerves .     421 

Spine  in  general 10 

Splanchnic  nerves, 480 

Spleen,  relations  of 172 

structure  of, 186 

sternum, 11 

?>tomach.  relations  ol 166 

structure  of, 177 


538  INDEX. 

Subclavian  artery,  left, ....,..,..,/.,.  325 

rig-ht, 299 

Sulci  of  brain, . . 393 

Superior  maxiliary  bone, ,  , 78 

articulation  of,    103 

Sympathetic  nerves, 476 

T. 

Tarsus,  bones  of, , 49 

lio-aments  of.. .  148 

Temporal  bone, - .  62 

articulation  of, , .    , 101 

Temporo-maxiliary  articulation 130 

Testes, ......... ......      194 

Thalami  optici, 406 

Thyro-hyoid  membrane -.  . .  199 

Thyroid  cartilage, 196 

Tibia, 45 

Tong-ue, 154 

Trachea, .........  203 

Trapezium  bone, 29 

Trapexoid      " 29 

Triang-le  of  Hesselbach 298 

Scarpa's, 267 

Trochanter,   g-reat^r. 42 

lesser, 42 

Turbinated  bone,  inferior, , 74 

middle 73 

superior 73 

articulations  of 105 

Tympanum, 505 

U. 

Ulna, 23 

Ulnar  artery  of  forearm.  ...    315 

of  hand 316 

nerve, 432 

Ureter 189 


INDEX.  539 

TTrethra',  female 493 

male 190 

Uterus. 490 

V. 

Vao-ina - 493 

Valves  of  heart, 207 

Valvulae  conniventes 180 

Vas  deferens, = 192 

Veins,  or  Vein  :  366 

axillar3^ 376 

azyg-os, 384 

basilic, 375 

cardiac, 385 

cava,  inferior, 269 

superior 383 

cephalic, 375 

cerebral, 377 

deep  or  comites, 366 

femoral , 267 

of  Galen 378 

iliac,  common 368 

external, 368 

internal 369 

inferior  cava 369 

innominate,  left 383 

rijrht 382 

jugular,  anterior, 377 

external 382 

internal '.   381 

popliteal,..        367 

portal , 36^) 

saphenrius,   lon^, 372 

short 372 

spermatic 371 

subclavian, 376 

ulnar,  anterior 374 

common 374 

posterior 374 


540  INDEX. 

Velum,  interpositum, 408 

Ventricle  of  brain,  third 408 

fourth 411 

lateral 405 

VertebrdB,  cervical, 3 

dorsal 4 

.lumbar 4 

peculiar, ..  5 

sacral 8 

Vesiculse   seminales, 192 

Vocal  cords,   true 199 

false, 199 

Vomer, 76 

articulations   of 105 

W. 

Willis,   circle  of, 365 

Winslow,  foramen  oi 165 

Wrisber^,  nerve  of 431 

Wrist  joint 127 

Zinn,   ligament  of 281 

Zygoma 62 

Zygomatic  fossa, 88 

muscles 280 


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